Feature/generalize parser

[geier1993]

This branch is based on the other PR with SFINAE capabilites for eckit::Translator - we may also just merge this one.

Changes in the branch require C++17 - before C++11 dependencies like metkit, fdb etc. have also compiled because compilers just emitted warnings. Hence PR for other repositories have been created as well.

Motivation:

• Abstract ObjectParser, JSONParser, YAMLParser with a template argument ObjectBuilder that is describing how to create an object. The trait ObjectBuilderTraits is checking for some requirements to describe the builder (will look nicer with concepts)..
• In Multio we have a new Metadata type that is not using eckit::Value and is more typed. For transport messages are encoded/decoded via JSON and hence having a decoder that avoids using eckit::Value is desired.
• As the whole "Parser" structure of the Object/JSONparser seems to be shaped by the YAMLParser, I also refactored the YAML parser - that comes with more specific requirements on the YAMLParser.

Changes:

• Most code has been put in header files with eckit::Value exchanged to specific calls to ObjectBuilder
• parseString is returning std::string as parsing is all about strings and sometimes string values need to be accessed directly (not hidden in a generic type) to handle keys or multiline strings.
• YAMLItem was a bit more complex than needed. I preferred to remove inheritance and Counted (attach/detach calls were very confusing and opaque to me). Now one class with tags (enum class) and a nested union is used.
  Moreover a std::deque was used to load items - however as only 1 item was loaded ahead, a std::optional is now used instead.

YAML fixes:

• single quoted strings '...' do not escape \ , \n ....
• Keys are always strings

With these changes, it is now also very simple to create custom value types (e.g. with std::variant) and replace configurations (if required at all).
I tried to to do a clean and sharp cut, if there are more things you think we should change let me know. The basic parsing logic is still the same.

[DJDavies2]

I'm getting a compile failure with this:

/home/d03/frwd/cylc-run/eckit-80/share/mo-bundle/eckit/src/eckit/parser/ObjectParser.cc:21:1: error: declaration does not declare anything [-fpermissive]
ObjectParser;
^~~~~~~~~~~~
/home/d03/frwd/cylc-run/eckit-80/share/mo-bundle/eckit/src/eckit/parser/JSONParser.cc:21:1: error: declaration does not declare anything [-fpermissive]
GenericJSONParser<parser::ValueBuilder, ObjectParser>;
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
gmake[2]: *** [eckit/src/eckit/CMakeFiles/eckit.dir/parser/JSONParser.cc.o] Error 1
gmake[2]: *** Waiting for unfinished jobs....
gmake[2]: *** [eckit/src/eckit/CMakeFiles/eckit.dir/parser/ObjectParser.cc.o] Error 1
/home/d03/frwd/cylc-run/eckit-80/share/mo-bundle/eckit/src/eckit/parser/YAMLParser.cc:21:1: error: declaration does not declare anything [-fpermissive]
GenericYAMLParser<parser::ValueBuilder, ObjectParser>;
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
gmake[2]: *** [eckit/src/eckit/CMakeFiles/eckit.dir/parser/YAMLParser.cc.o] Error 1
gmake[1]: *** [eckit/src/eckit/CMakeFiles/eckit.dir/all] Error 2
gmake[1]: *** Waiting for unfinished jobs....

This is with gcc 7.3.0

[geier1993]

I'm getting a compile failure with this:

/home/d03/frwd/cylc-run/eckit-80/share/mo-bundle/eckit/src/eckit/parser/ObjectParser.cc:21:1: error: declaration does not declare anything [-fpermissive] ObjectParser; ^~~~~~~~~~~~ /home/d03/frwd/cylc-run/eckit-80/share/mo-bundle/eckit/src/eckit/parser/JSONParser.cc:21:1: error: declaration does not declare anything [-fpermissive] GenericJSONParser<parser::ValueBuilder, ObjectParser>; ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ gmake[2]: *** [eckit/src/eckit/CMakeFiles/eckit.dir/parser/JSONParser.cc.o] Error 1 gmake[2]: *** Waiting for unfinished jobs.... gmake[2]: *** [eckit/src/eckit/CMakeFiles/eckit.dir/parser/ObjectParser.cc.o] Error 1 /home/d03/frwd/cylc-run/eckit-80/share/mo-bundle/eckit/src/eckit/parser/YAMLParser.cc:21:1: error: declaration does not declare anything [-fpermissive] GenericYAMLParser<parser::ValueBuilder, ObjectParser>; ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ gmake[2]: *** [eckit/src/eckit/CMakeFiles/eckit.dir/parser/YAMLParser.cc.o] Error 1 gmake[1]: *** [eckit/src/eckit/CMakeFiles/eckit.dir/all] Error 2 gmake[1]: *** Waiting for unfinished jobs....

This is with gcc 7.3.0

ah yes. I hoped that the new CI will compile some stuff for me without further effort.
Compiled with clang so far...
I may just remove the *Parser.cc files that have basically no content anymore.

[geier1993]

I still would like to use the CI for testing compilation with different compilers. However on the workflow it says than an reviewer has to approve it - but I think the workflow can be triggered separately from approving the whole PR?