Add more values to "tag_animation_direction"

[Altyrost]

... so the animation can be:

• left to right,
• right to left,
• top to bottom,
• bottom to top.

Curently there's 2 supported values: 0 would be left to right, and 1 would be bottom to top

[glxguard]

Would be better to make "horizontal", "horizontal reversed", "vertical", "vertical reversed", because you don't want your tags to move only one direction both when you're switching to the next tag and to the previous...

[Altyrost]

I'd rather having to assume that the second animation is the reverse of the one configured, rather than having to assume the direction of both. That's just me tho. The only way to not assume anything would be to make both configurable.