[WIP] Content Slider

This is mostly default non-minimized version of this work. Mostly default because some options (Next-Prev icons - captions for img) disabled for now.

Non-minimized version takes 25kb of space, while minimized version only takes 12kb.
Slider can be found at https://github.com/booncon/slippry

Signed-off-by: Antes <antes@simplemachines.org>
Should all the code below be in its own file?