Merge pull request #57 from janpolowinski/master

get docu changes
Merge pull request #69 from janpolowinski/master

merge master before new refaktoring sprint starts
[WIP] identity mapping roughly work again after refaktoring

+ clean up imports
[WIP] non-abstract handler for all P2GAMs
[WIP] clean explicit + calculated VM handling

using the P2GAM handler (but not in sub-mappings) ;
some use cases still don't work (e.g. AA-4).
[WIP] use P2GAM handler on submappings
Continue merging P2GAM code in handler

almost all test cases work again
merge + improve handling of explicit P2GAMs, clean up
clean up
[WIP] generalizing p2gam handling, fixing bugs
simplify P2GAM handler
improve example cit-1
[FIX] rdf:ID query returned too many results when called with subject constraint
combine P2GAM handler for top level and sub mappings
clean up P2GAM handler
add sub-mapping test
[FIX] passing subject / object constraints to referenced queries
comment statement extension as possibly redundant to mapping table extension
check labeling handler + clean up

+ clean up error handling
clean up parameter mapping