Escapes module names in EntryMethodHolderGenerator.

A previous change started requiring that module names double as
valid Java class names, but this was found to be too restrictive
since so many modules include the '-' character.

This change removes that restriction, adds general purpose
String -> Java class name escaping and uses that escaping when
generating EntryMethodHolder classes based off of module name.

Change-Id: I8d47d86a94e9e37aaf184e24e546253e920bc987