Unsupported nodes are now called unsupported IR nodes
Renaming of NodeInfo to VdmNodeInfo
Added class to hold IR node related info
Introduced the notion of unsupported target language nodes, i.e. nodes that are supported by the IR but not the backend/target language
Updated JavaCodeGen to add info about unsupported target language nodes into the generated modules
Updated JavaCodeGenMain to only output the name of generated quotes as well as information about unsupported target language nodes
Added the time expression and the periodic statement to the IR. However, these nodes remain unsupported in the Java code generator
Updated the frontend of the Java code generator to conform to the most recent work on core/codegen

Now the Java code generation plugin also outputs information about IR nodes that are not
supported by the backend
Merge remote-tracking branch 'origin/gk/codegenconc' into pvj/main
Left some legacy code as commented
Deleted test that is not needed since concurrency of static operations is not supported by the Java code generator
Added functionality to fetch the approximated (VDM node) location of an IR node.

Now The JavaCodeGenMain also outputs this location for convenience.
Minor fix: State change notifications were not appearing for assignment statements in the thread definition