[gtk] add Esc image button to exit from executing
[lexi-state] remove unused data fileds in lexicon_states
[history] aging all history infos into long term at the beginning
[lattice] transfer every ENDING_WORD in language model

  no matter if the previous lattice state begins from 0.
[gtk] set candidate list size to 5
[python] change to use python2.* in the python scripts

   python3.* changes a lot in print symantics and gtk module
  useness.