new frontend option 'featureConfiguration' added
this option needs 1 argument, which is the path of the featureConfiguration file, for example BusyBoxDefConfig.config

After creating the ifdeftoif option struct, there now is an init function which uses the featureConfiguration file to assign the values '0' and '1' to ifdeftoif features

The main or 'filename' + "_main" function calls the above mentioned function to assign values to the ifdeftoif features.
Merge remote-tracking branch 'origin/master'
missing FrontendOptions import, from merging I guess
frontend option bugfix
Added check for possible invisible enums after extraction.
Removed linked function pointers from parameter list.
Clean up
Merge branch 'jl'

Conflicts:
	CRefactor/src/main/scala/de/fosd/typechef/crefactor/backend/engine/CExtractFunction.scala
Clean up after merge.
fix several intellij warnings
fixed a severe bug in computeNextRelevantFeatures, a list of featureExpressions was collected and during one calculation only the head of that list was used for further calculations instead of the whole list.

This fixes TypeErrors in top.c @busybox/procps
Merge remote-tracking branch 'origin/master'
fixing several intellij warnings
refactoring; code layout
code layout
renaming refactoring
change return type of inline function from TranslationUnit to Either[String,TranslationUnit]; this way we support proper error messages
use config.properties error messages in CRenameIdentifier
renaming refactoring
code layout