tried to get rid of pre-defined constructors by defining a special prelude. (to be replaced by module system) but at the moment, the typechecking wonts wok.
now all tests work for parboiled parser
brought combinator parser up to date. tests seem to work.
Pflichtenheft hinzugefügt
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
Merge branch 'master' of github.com:SL2Team/sl2 into externdefs
Merge branch 'module_serializer' of github.com:SL2Team/sl2 into prelude
prelude stub compilation results in prelude_stub.js
Merge branch 'prelude' into externdefs
Merge branch 'prelude' of github.com:SL2Team/sl2
changed compilation driver so that it writes the compilation results to files instead of the console. (it also generate the json code)
Merge branch 'master' into externdefs
EXTERN zu syntax hinzugefuegt. also: IMPORT EXTERN "blubb" und DEF EXTERN bla = "blubb" zum abbilden von funktionen auf js funktionen...
external defs syntax working...
changed characters that are used to represent special characters so that the generated names are "more intuitive". (e.g. $e$e for ==, $p for +, $d for / etc.
 * added basic support for loading imported modules (so that they can be used for checking and code generation)
 * added code generator effects for external definitions and imports.
added module import stubs
Merge remote-tracking branch 'origin/master' into module_import