1.2: KiCad 8.0

• ERC and DRC are now supported by KiCad 8.0 and so included as targets, including the an option flag to exit with non-zero status if failing. make sch and make pcb both build the report files. make rules just performs the ERC and DRC.
• KiCad 8.0 also now includes a built-in BoM tool kicad-cli sch export bom. It is now the default rather than KiBoM. KiBoM is still supported with the BOM_CMD as previously.

Closes #1 .

Full Changelog: v1.0...v1.2