keepassx2pass: friendly title field

This patch removes several special characters while attempting to preserve
as much meaning in the filename as possible. These changes are made to the
KeepassX title before it is used as a file password store filename:

   - Spaces between words in file names are replaced with camelCasing.
   - The characters \ | ( ) are each replaced with a hyphen.
   - Trailing hypens are removed.
   - @ is replaced with "At"
   - ' is removed