Make FMVPlayer in TD use a completely black background

Fixes #6211.
Make FMVPlayer in RA use a completely black background
5936 Advanced Power Plant have a different layout in the original
Merge pull request #6230 from havok13888/AdvancedPowePlant

#5936 Advanced Power Plant have a different layout in the original
Merge pull request #6220 from obrakmann/fix6211

Make background of FMVPlayers in TD and RA black
Convert damage modifiers to integer percentages.
Convert speed modifiers to integer percentages.
Convert firepower modifiers to integer percentages.
Rename ProneSpeed to SpeedModifier in TakeCover.
Upgrade mod rules.