Fundamental changes in parser and compiler.

Parser:
  * grammar sticks closer to simplified ACT-R grammar as presented in master thesis, p. 51
  * parse tree uses Prolog lists for lists of productions, buffer tests, slot tests, ... instead of self-made lists (better readability, compactness)
  * cut operator to limit needless backtracking

Compiler:
  * recursive Prolog-style parse tree traversal with several accumulators is replaced by CHR-based solution which collects slices of CHR rules and puts them together. Shorter code, better readability