Re-introduced operation post condition obligation in PogParamDefinitionVisitor for implicit operations to make pog-string-based tests pass (this is how VDMJ does this). This is, however, not really needed since this is already captured by the satisfiability obligation and thus it is redundant.
Merge branch 'origin/kel/astv2'
Merge branch 'origin/kel/astv2'
Merge branch 'origin/kel/astv2'
Merge branch 'origin/assistant-rewrite'
Merge branch 'origin/kel/astv2'
made the type wider using the ast generated interfaces
extracted the set state out from the generation of implicit pre and post definitions
moved rootvisitor field to base class. It should be removed but the conversion of utility functions which still required this concrete type and not just the interface needs to be corrected first.

added functionality that makes all unknown node applications delegated back to defaultnode in the root visitor
added new experimental test framework version for junit 4 - currently being used in compass by the type checker
added initial static access for type definitions when created in the factory
updated ast-creator version to version 1.5.0
updated dot to support multiple nodes and have filters and better set of main dot bin file
removed unessesary nesting for defletdetstm -> letstm

changed arguments from concrete types to interfaces in astfactory and pog
commented explicitly failing test. It was empty but make mvn test fail
changed the type checker such that is can be customized by compass
change astfactory method to use interfaces instead of concrete classes
improved tostring used in the AST
updated the type checker to make proper used of the assistantfactory and make it possible to parse a factory to the ClassTypeChecker
improved extensibility of the type checker by changing static calls to use the factory
changed concrete type of type check to its interface