done until class variable aware mapping
parsing rules in mappings - ongoing
add test case for meta mapping
first version of meta mapping expander
almost finish the feature of meta mapping

1. the junit test is passed
2. the code needs to be refactored and well documented
refactor and document the MetaMappingExpander class
Merge branch 'develop' into feature/variableClass
add first version of MappingSplitter
refactored a bit
move the URI templates handling into a seprate utility class
add test case for meta mapping with variables in the predicate of the triple

Now the test case fails because of the parser
now TurtleOBDA parser can parse mappings with variables in the predicate
now MetaMappingExpander can handle variables in the predicate of the triple
Merge branch 'develop' into feature/variableClass
try to replace uriconstant.tosSring by getValue
fix the bug with unnecessary quotes around <uri>
generated parser
merge branch feature/variableClass to develop
regenreate lexer and parser of Turtle OBDA