Johannes Mey authored Oct 30, 2019 and René Schöne committed Oct 30, 2019

Implement JSON pointer (built-in) and manual pointer treatment with two examples (JSON pointer and relative JSON pointer)

- Changed error message for invalid redefinition

- Also add some tests for left direction

- Extended grammar to let TypeDecl and Relation have filename
- Extended error message to display and order first by filename
- Added testcase with multiple inputs having errors

- Simplified lexer, dropping lexical state String
- Added test case for this scenario (copied from MultipleFiles)

make unresolved subtypes of abstract types abstract, use unresolved interface. rename resolver methods (for MQuAT compatibility)