TTC example: corrected edge marker in Rule Multiple...
Rule validation: improved consistency check between DPO semantics and
rule markers
Improved coulouring: created elements have green forground coulour
removed console output for testing
retrieval of known markers for rules in RuleUtil.java
Translation Button: removed export of intermediate XMI file
Interpreter - modified attribute check: added check that attribute value
is not null, i.e., attribute can only be matched, if it is set