[GSOC-UPDATE] Impress Remote

[Andrzej J. R. Hunt]

Hi all,

The latest from today:

-Basic caching of preview images, and image updating on slide change 
(untested until server starts sending this data).
-Added transmitter with command queueing to the server.
-Fixed threading and mutex issues in the above.
-Fixed protocol parsing bug in the server.
-Slight cleanup of the Server/Receiver/Transmitter hierarchy.
(-Learned some things about how LO GUIs are written.)

Cheers,

Andrzej