SEGZONE types were confusingly named PCB_ZONE_T. Zones in pcbnew are
now _only_ PCB_ZONE_AREA_T, so we name segzone types PCB_SEGZONE_T to be
clear.
This also removes processing of the SEGZONEs from connectivity
calculations.
(cherry picked from commit b3a5e08c2f)
Includes some dialog changes to go with the menu update.
Includes promoting the Pcbnew graphics mode back to main menu.
Includes renaming Graphics modes to Toolsets.