import statement added to parboiled parser; still buggy
Merge branch 'parser' of https://github.com/SL2Team/sl2 into parser
tests were fixed externally by benkeks, while I didn't push my changes
import directives are now being parsed successfully
changed int and real token definition to accept negative numbers (Parboiled only)
removed parser tests that expect unary minus to work (except as part of a numeric token)
now all tests work for parboiled parser
brought combinator parser up to date. tests seem to work.
parser modifications for prelude refactorization
Merge branch 'parser' of github.com:SL2Team/sl2 into prelude

Conflicts:
	src/main/scala/de/tuberlin/uebb/sl2/impl/ParboiledParser.scala
prelude stuff