classicons: bug fixes and optimization

see also https://github.com/haste/oUF/pull/210
classicons: call for an update from ClassPowerEnable
classicon: use SPELLS_CHANGED only if in the required spec or the required spell is unknown
classicons: fix indentation

Thank you Atom ... NOT
classicon: aaaaaand ... whitespaces again
classicons: remove the PostVisibility hook and call an update on disable so layouts can hide additional stuff
classicons: do not re-show segments after disabling the update

propagate the event to :Pre|PostUpdate
do not en/disable when already in the same state
classicons: left over print removed
classicons: add the UpdateTexture hook to the documentation
classicons: DARK_FORCE is not used anymore
classicons: let the layout deside how many widgets they define
classicons: do trigger an update on ClassPower{Enable|Disable}
classicons: allow for Visibility to be overridden
Merge branch 'Rainrider-classicons'