Adding a dependency from a java_library to a scala_library, this should not trigger the build dependency missing warning.

Jmake's analysis file only contains the dependency class names, not the full path to the class file. This means it assumes
they are in the compiled java directory, meaning we get missing dependency warnings for scala files.

Changed to pick those up in the correct classes directory.

Reviewed at https://rbcommons.com/s/twitter/r/474/
Fix the analysis case for when a scala_library has a java_source that depends back on the scala_library

Reviewed at https://rbcommons.com/s/twitter/r/507/

Conflicts:
	src/python/pants/tasks/jvm_compile/jvm_dependency_analyzer.py
Relativize java classpaths relative to the build root

JIs original relativization code didn't work because java was executed with subprocess.call, and this call was given a different cwd argument (the build root) than the user's actual current working directory. I have made the classpaths relativized relative to the build root as opposed to the current working directory, and this seems to work.

Also added classpath length logging (so we can know when we are getting close to the maximum argument length).

Testing Done:
./build-support/bin/ci.sh all tests passed

Reviewed at https://rbcommons.com/s/twitter/r/516/
Fix the bad merge of b3d93962ca01d62ccf3d236a6952da8a3530d24a, apparently java_sources can be None
c2
c2
c2
c2
c2
Merge branch 'twitter/release' of https://github.com/pantsbuild/pants into twitter/release
c2
c2
c2
Merge branch 'twitter/release' into ji/twitterrelease2