Make Translators that work in Java part of gremlin-core

Translator instances have lived with their GLV implementations for the language they represented. This led to us deprecating the PythonTranslator which lived with gremlin-python as Jython support was being deprecated out. The Translator functionality is helpful though and it's a shame to lose it as a lot of times we give an answer in Groovy and translating to Python takes some manual effort. If we organize translators differently so that each language gets translators to other languages then we give users the functionality they need to more seamless move from one GLV to the next.

For this change we will move the deprecated PythonTranslator and the GroovyTranslator to gremlin-core as that module is the one for "Gremlin in Java". GroovyTranslator will be deprecated from gremlin-groovy.