improved error handling
Merge branch 'master' of https://github.com/SL2Team/sl2

Conflicts:
	src/main/scala/de/tuberlin/uebb/sl2/impl/ModuleResolverImpl.scala
	src/main/scala/de/tuberlin/uebb/sl2/modules/TopologicalSorting.scala
	src/main/sl/examples/main.js
a small part of the report ...
added `neg' function  (negation) to prelude, because I want to note it in the
report as our alternative to the unary minus.
Merge branch 'master' of https://github.com/SL2Team/sl2

Conflicts:
	doc/report/report.pdf
	src/main/scala/de/tuberlin/uebb/sl2/impl/MultiDriver.scala
	src/main/scala/de/tuberlin/uebb/sl2/modules/TopologicalSorting.scala