Improve Windows install

[stain]

Assuming #166 then ProvToolbox works in Windows. However installation is still difficult as the user needs to install OpenJDK and Graphviz, which can be bewildering due to their diverse websites and lack of guided installation instructions.

I've created https://practicalprovenance.wordpress.com/2020/12/02/installing-provtoolbox-in-windows/ and added it to the https://github.com/lucmoreau/ProvToolbox/wiki/Installation wiki under a new Windows section. I found in particular the https://adoptopenjdk.net/ options much easier than other alternatives.

Perhaps it would be possible to bundle OpenJDK JRE and Graphviz in the binary? We used to do both for the Taverna Workbench 2.5. In case you are interested, see https://github.com/taverna/taverna-workbench-product/tree/core/src/main/install4j - note that AdoptOpenJDK didn't exist then so we had to use a dubious build of OpenJDK for Windows and and old dot.exe