Added generic value provider for custom callbacks.
Added generic value provider for custom callbacks.

codeaudit/myriad-toolkit,TU-Berlin-DIMA/myriad-toolkit,TU-Berlin-DIMA/myriad-toolkit,codeaudit/myriad-toolkit,TU-Berlin-DIMA/myriad-toolkit,codeaudit/myriad-toolkit,codeaudit/myriad-toolkit