prep work to support one-char variable namepaces
work a bit toward string handling unification
refactor: somewhat simplify property-name-to-id mapping
refactor: more simplification in property handling
refactor: use common code for message property description processing

in all cases except script var access -- this comes next...
refactor: simplify JSON variable access
fix potential segfault introduced by last refactoring
remove no longer necessary cases
refactor get.*PropVal() series of functions
refactor RainerScript variable access
refactor: remove now no-longer needed functions
minor cleanup
refactor: align jsonFind() calling interface with recent changes
fix small memleak introduced during refactoring
fix another small memleak introduced during refactoring
improve debug output

we know also learn variable type
enable error message for invalid property names

also add some support for global vars back, as the syntax
may not go away.
fix refactoring regression: make message and system properties work again in script
fix VAR handling in script grammar and code

The $-var designator is now correctly stripped off the varname.
bugfix: unset statement always worked on message var, even if local var was given