Java build

[jenow]

What does this PR do ?

Builds a JAR file for the Java SDK using gradle

How should this be manually tested?

run make java in internal/wrappers/build/java and see if kuzzlesdk-1.0.0-sources.jar and kuzzlesdk-1.0.0-javadoc.jar are present in internal/wrappers/build/java/build/libs

Note

This does not build multi architecture JAR file. This will be done in another PR which will deploy the JAR's files on maven

[codecov-io]

Codecov Report

Merging #147 into 1.x will decrease coverage by 0.09%.
The diff coverage is n/a.

@@          Coverage Diff           @@
##            1.x    #147     +/-   ##
======================================
- Coverage    89%   88.9%   -0.1%     
======================================
  Files       244     244             
  Lines      4382    4382             
======================================
- Hits       3900    3896      -4     
- Misses      451     455      +4     
  Partials     31      31

Impacted Files	Coverage Δ
realtime/subscribe.go	71.42% <0%> (-5.72%)	⬇️
realtime/join.go	72.97% <0%> (-5.41%)	⬇️

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[jenow]

I put this PR in wip because I need to organise the generated java source files as a real java project otherwise we can't publish it on maven as by default the publisher is looking for a src/java/main project

[Aschen]

I had some trouble to manually test this PR and build the java SDK.

• Install swig
• Install JDK8 (not compatible with JDK9)
• Set JAVA_HOME

Maybe it can be useful to document the dependencies (or step) to achieve a java sdk build ?

Otherwise, the build is here internal/wrappers/build/java/build/libs/ and not here internal/wrappers/build/java/libs/