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.
Don't try to use complex algorithms taking into account default
margins, line-widths and pen-widths (especially when they differed
between label types). We now use the (user-controlled) text
offset ratio to determine the margins (from the center-point of
the attached line).