Extract java backend and dependencies to new repo

It's now in idris-hackers/idris-java, but I can't promise it works.
Merge branch 'master' of github.com:edwinb/Idris-dev
More sensible hash function for specialised names
Fix transforms under lambdas

Need to ensure names are in the same form (P or V) on both sides of the
transform!
Merge branch 'master' of github.com:edwinb/Idris-dev into partial-eval
Merge pull request #1679 from edwinb/partial-eval

Partial evaluation improvements