lsif-java: cross/same-file references (prev. same-file only)

[efritz]

Working for:

• variable type (incl class properties+args)
• variable uses (incl class properties+args)
• class instantiation
• method invoc
• method references (aka obj::method)

[Strum355]

Current WIP issue #53

[Strum355]

Closing as considered complete and working. May need to be expanded to support more constructs, but the logic exists and works for all currently supported
(by lsif-java) constructs