Removed "Unloading Cells..." text from the loading screen.

OpenMW unloads the cell so fast, it's not really possible to see this
message. It's annoying to see the loading text switch rapidly from
"Unloading cell..." to "Loading cell..." in just a single frame every
time a cell loads.
Merge branch 'stuff' of https://github.com/vorenon/openmw into stuff