[cmake] search for Qt4 in global file, fix translations

* MyQtTranslation.cmake: uses add_custom_target instead of add_custom_command;
  prevents modified source files from getting deleted on "make clean"
  Provides custom target "update-translations"
* option UPDATE_TRANSLATIONS to automatically update translations before
  each build
[nuts] replace bison parser with recursive descent parser

a few more lines of code, but should be more readable and result in
better error messages.
also the old parser had shift/reduce conflicts...