Reworked CompactNode more towards model instead of pure string templates.

Further:
* removed headKey(), headVal() API
* generated code now has less unchecked conversion warnings
More refactoring + re-energizing 'untyped' option.
Supporting key and value types as arguments (instead of hardcoded version earlier).
Supporting generation of various configurations simultaniously.
Small layout corrections, etc.
Sketching support of methodsWithComparator() option.