Added some expression tests to exercise generation of the is_ expression
Added tests to exercise generation of the is expression for more complicated cases
Updated the Utils class to support generation of the is_ expression
Slight improvements to some existing test results
Added support for the 'is' expression in the IR with support for basic types, tokens, tuples, records and classes
Added templates to support generation of the 'is' expression
Set default code generation dialect back to VDM-PP
Import cleanup
Updated the JavaFormat class with utility functionality to support code generation of the 'is' expression
Fix: Pre and post conditions were never removed from the object initializer method