1) Generalize SCH_ITEM owners (SCH_COMPONENT, SCH_SHEET, and now
SCH_GLOBALLABEL)
2) Generalize hypertext items
3) Use SCH_FIELD autoplace infrastructure for placing intersheet
references
4) Use textVar infrastructure for buildin intersheet references.
As an important side-effect this also fixes the undo issues with
intersheet refs.
CHANGED: In Schematic Setup->General->Formatting->Connections, added
pulldown for "Junction dot size" with values none, smallest, small
default, large, largest" Added support in "sch_painter.cpp" to not
paint junction when they have a diameter of "1" which is what "none"
sets as the diameter.
CHANGED: Remove wire and bus formatting GUI elements from "Schematic
Setup" dialog panel. Wire thickness is handled by netclasses now
and this was a leftover from before that change.
Fixes https://gitlab.com/kicad/code/kicad/issues/5815
Also fixes a bug where a bunch of eeschema settings weren't getting
loaded because it looked like they were larger than the max value
(which wasn't being scaled from mils to internal units).
Fixes https://gitlab.com/kicad/code/kicad/issues/2089