Normalize usage of term "Grammatik" and "Sprache".

Grammatik:
  The special notation used in language theory.
Sprache:
  A (possibly infinite) set of words.
Specify that n^k^m is (n^k)^m  (ie. left-to-right evaluation).
Put function definitions at same page like their usage.
"turing-berechenbar" becomes "Turing-berechenbar"

Proper names are written with capital letters.
Extend roadmap.