Pep-8 cleanup. Ran pylint and pyflakes over keepassc and fixed the errors.
Mostly involved just formatting changes.

* There were a few variables defined that were never used, so those got
deleted.

* I changed the 'from curses import *' and 'from kppy import *' to either
specifically import needed classes by name (kppy) or defined an alias
(curses=>cur) so it's easier to see what methods/functions are from which
modules.
Added j/k navigation for database/keyfile open menus. Moved the option
to open the last opened database to first in the list.