missingletter, fixed the number of level in the config box

There was an off by one and the last level was not displayed
in the configuration dialog box.
imageid, reworked to use images from lang/words
missingletter, fixed support for more then 6 letters.

If more than 6 letters choices were proposed they was not
displayed at all.

Fixed a little memory leak.

Improved the layout to support more than 6 letters.
missingletter, reworked to use images from lang/words
lang activity, minor visual improvements.
Updated Slovenian translation