Fix of keybindings help window in overmap and ranged screens.

1. Added borders.
2. Fix ranged help strings overlapping.
3. Add ESC key to menu exit.
4. Fix help window showing after user leave help (q,Q,ESC is pressed).
About this fix.
Before:
![help-before](https://f.cloud.github.com/assets/5244047/1684242/b6622ab6-5dc8-11e3-9c6e-54cdcdb66044.png)
I fix than.
But ranged help win still have problem. Yes help window is cleared. But some parts of screen not redrawing.
After fix. help win is opened:
![ranged-help](https://f.cloud.github.com/assets/5244047/1684269/08b49650-5dc9-11e3-8ac1-a7fcf9cb9ef9.png)
And after closing:
![ranged-help2](https://f.cloud.github.com/assets/5244047/1684284/1aa8bbf2-5dc9-11e3-82fb-a0d8c9709fd0.png)
Sorry for MS Paint madskills.