Set up a new lineage for SCH_ITEMS to get back to the SCHEMATIC
they live on: Items will all be parented to the SCH_SCREEN that
they are added to, and each SCH_SCREEN will point back to the
SCHEMATIC that it is part of. Note that this hierarchy is not
the same as the actual schematic hierarchy, which continues to
be managed through SCH_SHEETs and SCH_SHEET_PATHS.
The RTree does not have a deterministic iterator, so extracting items
may be in arbitrary order, causing issues as the schematic appears to
change when comparing to previous revisions.
This uses the SCH_ITEM comparison operator to for ordering by type, then
by custom sorting within type.
For the netlist, we choose the first available unit in the sheet for
each component.
Fixes#3811 | https://gitlab.com/kicad/code/kicad/issues/3811
This also removes vector cover types which do nothing except obfuscate
the underlying implementation.
Mainly changes SCH_SHEET_PINS and CONFIG_PARAM_ARRAY (which will soon
be replaced by Jon's new stuff).