The generated CreateX() calls now come with default values for args.

bug: 15777627
Change-Id: I9389de46ea883ab0ef1beab9370e5c8e96b4d0b5
Tested: on Windows and Linux
Made Java argument names help remind the user when something is an offset.

Bug: 15856217
Change-Id: I9163d13ca26c2d53064f5289c993692be711685f
Tested: on Windows
flatc can now convert flatbuffer binary files into json.

Also removed it appending _wire to filenames, renamed the json golden
file to .golden to not clash with generated files.

Bug: 15781201
Change-Id: I8322861e50d1e5b6a5ab5e4b5e5d8ae13c356eb2
Tested: on Windows and Linux