[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 used in this place: https://github.com/booncon/slippry

Signed-off-by: Antes <antes@simplemachines.org>