added module import stubs
Merge remote-tracking branch 'origin/master' into module_import
refactored model importer (now model normalizer)
added module normalizer method stubs
partial implementation
implemented module normalizer

note that the identifiers of actual FUNs and DATAs can not be
substituted
for instance: FUN foo : <Type>
will not translate to FUN <module>.foo : <Type>
added module context support

this implements a function which builds a context for modules which can
be used for type checking
converted tabs to whitespaces
removed debugging println
corrected a wrong test in parser spec for handcoded js.
corrected an error related to ast merging that has been fixed in choeger/sl2 (we dont currently use the function... just in case we start using it again, it might be cool if it worked as expected.. :))
made some type checking tests work without imported prelude.
cleaned up prelude files
made DEF EXTERN identifiers accessible from within a module...
complete preliminary prelude code
added hello world example using qualified imports
fixed some path issues in moduleresolverimpl
formatting of prelude.sl.signature...
added imported context to type checking
module resolver quite integrated