Add animations and .gif support

[shellixa]

Add support for simple/basic animations such as:

• bounce
• shake
• spin left/right
• pulse fade

...and automagically export these icons with their animations as a .gif-image.

Will probably not be implemented for a long time

[sebinside]

Yes, I would argue that this has very low priority as animated icons are more of a gimmick and an anit-pattern as they steal your attention instead of speeding up your workflow.