Add some attention to color-coding of files, outliner sequence tab

[MichailSoluyanov]

For now outliner’s sequence tab is missed for attention. If you look at it, you will note a problems:

1. Wrong icons:

2. Strange color coding:

But sequencer already has color coding:

Why do not use it in all spaces?
Outliner:

And of-course file browser:

[Draise]

Great observation. These should be made into tasks.