Params for LLScrollListCell, LLScrollListItem, and LLScrollListColumn
Moves code block for creating a LLScrollListCell out of LLScrollListCtrl::fromXML and into LLScrollListCell::create
Removes mDefaultListTextColor from LLScrollListCtrl, it is now used only in LLScrollListCell::create
Adds LLScrollListCtrl::addRow and LLScrollListCtrl::addColumn functions that take these Params
Separators are now built from an icon.. we may want to tweak it in the future, looks alright though
LLFloaterAvatarList::refreshAvatarList now builds elements with these Params instead of by LLSD
