Add lib-serialization and add integration tests for all filters

add lib-serilaization and update code

fix failing json merge tests

funny buisness with FileLocation "out" directory...

just use "in" directory for everything

begin adding serialized output to integration tests

add serilaized tests for roundtrip...

begin to enhance proto model and fix problems

add AltTranslation and Note

fix handling of multiple segments

several small changes to account for null fields in protobuffer...

all roundtrip integration tests now pass

add serialized format for simplified tests

update golden values for unit tests

full rountrip support for notes, AltTrans...

fix some tests with incorrect method calls add or update xliff compare files add some helper code to Note and AltTrans classes

Create TextUnitMergerSerialized and fix any errors found. Integration tests now use both xliff and proto for testing.