AppSettings: Unbind "switch zoom" by default.

Rarely used feature, but easy to accidentally activate in which case it will confuse users.
Losslessly compress res/web/img.
Whitespace cosmetics.

Remove unneeded spaces and reindent comments in some cases to improve readability.
Update Changelog.txt.
pre-commit.sh: use 2 spaces for indentation.
PlayerSeekbar: thumb paint optimization

Painted thumb is now cached
PlayerSeekbar: code refactoring
PlayerSeekbar: allow frame numbers in the tooltip

For media that uses frame numbers for seeking, for example .swf
IMediaSeeking::GetTimeFormat refactoring
Options Dialog: properly gray-out inactive items

Refs #2449
MainFrm: don't hide window when changing tray icon

Fixes #3391