Schematics refactoring: - New sheet reserved to video memory. - Removed video memory parts inside video_generation. - Removed video memory parts inside GPIO. - Generic cleanup to keep all circuits inside each sheet.

Notes and minor fixes

Partial signal renaming

Z80 halt controls the RUN LED

Found WR signal and fixed RD

Found both ROM CE and OE

Fixed addr order in mem mux, busack on z80 buffers

Fixed address connection from Z80 to buffers

Upgraded to kicad 7

Added bus buffers (or their placeholders) to z80cpu schematic