Rename repository to reflect wider scope than just observer API

[objectiser]

As discussed in this thread (#3 (comment)) we should rename this repo to something more appropriate to cover observer and filter API.

java-patterns - too generic
java-tracer-decorator and java-tracer-wrapper - I think these are too implementation specific, and focus just on the wrapping/decorator rather than on the APIs
java-api-extensions and java-tracer-extensions - these are in the right direction, wonder if a truncated form would work - e.g. java-ext

[pavolloffay]

The most I like is
java-api-extensions. java-ext is not story telling at the first glance I don't know what is there.

[yurishkuro]

why not simply use different repos?

[objectiser]

@yurishkuro Was thinking that the filter/interceptor API would also use the SpanData to enable more interesting possibilities.

[yurishkuro]

It's it worth creating intermodule dependencies because of one pojo?

[objectiser]

The APIs should be in a single module, but the wrapper discussed in #5 would probably be better in a separate module.

[objectiser]

@pavolloffay @felixbarny @yurishkuro As part of this issue, would like to do the following:

• Rename the repo to java-api-extensions (as proposed by Pavol)
• Artifact id changed to opentracing-api-extensions
• Place interfaces into package io.opentracing.contrib.api

Any objections?