DeskClock: update czech translation

I shortened the Reset button string as it doesn't fit
into button on my P990 with default DPI.

This will look much better.

Patchset 2: added missing strings and arrays
Patchset 3: fixed translation for alarm dismiss

Change-Id: Ie982a3c0c8cdbf5afe9240a2a8c43ca69f8ac132