Saw that layout really should be separated from the style struct, so went ahead and pulled the trigger...
A bunch of other refactors have also been done
* Lifted layout out of style, its not separate in UI_Box and in UI_State there is not a UI_LayoutCombo stack.
* UI_StyleTheme renamed to UI_StyleCombo
* UI_Theme has both UI_StyleCombo & UI_LayoutCombo
* Made files for the "project" related code
* ui_layout_compute moved to its own file, ui_layout now used for layout related data structures and interfacing
* Impovements to horizontal & vertical box impl
* UI_Box now keeps track of how many ancestors it has
Biggest win was getting the intial fixes for overlapping boxes.
Eventually I'll need to add support for sorting actives of top-most ancestors
(pretty much just remove from linked list and add to last position (adjust indices of adjacent and new top most, etc)