Revert "Engine: restored bitmap reading/writing from/to saved games"
Revert "Engine: restored bitmap reading/writing from/to saved games"

+Added small fix for 15-bit bitmaps instead

This reverts commit 280b8979abb2c207f192acb673242a4e9842dc11.

OutOfOrder/ags-geminirue,OutOfOrder/ags-geminirue,OutOfOrder/ags-geminirue,humble/ags-geminirue,OutOfOrder/ags-geminirue,humble/ags-geminirue,humble/ags-geminirue,OutOfOrder/ags-geminirue,OutOfOrder/ags-geminirue,humble/ags-geminirue,humble/ags-geminirue,humble/ags-geminirue,OutOfOrder/ags-geminirue,humble/ags-geminirue