Support simple primitives for icon animation

[jbergstroem]

..would be pretty sweet to have an animated cog when compiling node, hey? 😄

[dfrankland]

So the icons in the tab are icon fonts, so the only way to do this would be to use simple CSS animations. There'd be no way to do animated cogs (multiple interleaved teethed cogs), unless we switch to gif or something else.

[jbergstroem]

I was thinking of just using css animations but found no good way of adding an activeStyle per icon.

[jbergstroem]

How about

config.tabIcons.mapActiveStyle: {
  'gcc': 'animation: spin1 2s linear;'
}