Merge branch 'feature-omit-palette-definition' into feature-optimize-data-size

Conflicts:
	src/tosixel.c
Merge branch 'master' into release-1.2
Merge branch 'hotfix-fix-segfault-on-quit-animated-gif' into release-1.2
Update ChangeLog
Bump version
Merge branch 'release-1.2'
Merge branch 'master' into develop
Accepts sixel as input format by img2sixel
Merge branch 'feature-optimize-data-size' into release-1.3
Merge branch 'feature-load-sixel-as-input-format' into release-1.3

Conflicts:
	ChangeLog
	converters/loader.c