Revert "Handle keys only after stock GTK already handled them itself."

This reverts commit e1c4c25b290af171dd19fd6b3b20ee3fc737dce0.
Apparently, some keys no longer work with connect_after, e.g. space.

git-svn-id: svn+ssh://svn.code.sf.net/p/mcomix/code@922 ef8490bc-f317-4725-81ed-e95a9aca1bcf
Add button to reset all keys to their default binding.

git-svn-id: svn+ssh://svn.code.sf.net/p/mcomix/code@923 ef8490bc-f317-4725-81ed-e95a9aca1bcf