EDA_ITEMs are responsible for giving their parent a crack at it if
they failed to resolve it. This recurses all the way up to the schematic/
board, and then to the project.
Cross-reference handling is also move to the EDA_ITEMs. It must be done
before bubbling up so that we don't end up in loops. (The aDepth parameter
will break the loop, but without having done anything useful.)
Fixes https://gitlab.com/kicad/code/kicad/issues/13541
CHANGED: The text variable ${SHEETNAME} now always represents the name of the
sheet when used anywhere in the schematic editor, including the title block
ADDED: A new text variable ${SHEETPATH} which is replaced with the path to the
current sheet - e.g. "/Sheet 1/Sheet 2".
To ensure backward compatibility, the default drawing sheet now uses
${SHEETPATH}. Custom drawing sheets will need to be manually edited.
Seth Hillbrand
Jeff Young
Roberto Fernandez Bautista
Jon Evans
Jonathan Haas