Document a bit.

Change-Id: Ic62acc3eeb4e3526cc6b7366f51f5f3bf69528c1
thumbnails: Consolidate code.

There were 2 copies of the thumbnailing code; consolidate that to one copy
directly in VCL.

This kills the attempts to do alpha channel that used to be in the VCL copy of
the code - it was producing wrong results, the bitmaps ended up empty.

Change-Id: I415c410c287a95e75293bdcba5d71083d1d01dc1
thumbnails: Provide the size as a default parameter.

And increase it consistently to 256 pixels.

Change-Id: I123e11d597269d7e43298504f1dbd0098c9b0149
thumbnails: bSigned is always false, nobody uses the signed sign, kill it.

Not killing the icon itself, still seems to be used by on Windows in the shell
code.

Change-Id: I21c3b1ae6dfc65b6852659d6157b02324a485774
thumbnails: Nobody uses the overlay functionality now, kill it.

Change-Id: I74c463b67dd950a3e4de838ed0dc55ec366ab8a7
startcenter: Kill the old branding images.

Change-Id: Idab983ac085efa755025fdef1caa2c0073dd1ba0
startcenter: Don't cut off the thumbnails.

Change-Id: Ie5ad5f5be48aa873df94a31e980aaabc4ac24868
fdo#72338: startcenter: Show busy mouse pointer when starting apps.

Change-Id: I8f254419ea7bb4e3e9835bd9fab8229ed89cd0e9