Endstop adj updates

Check that endstops are within 2mm of each other before allowing
autocalibration (prompt user to fix hardware)

Added check for endstop_adj values > 0 during autocalibration
Added Z-Probe accuracy check
Fix issue with Z-Probe accuracy check
Added multiple Z-Probe function for error detection
"double tap" and build height/endstop updates
bug fixes
Autocalibration updates
bug fixes
Autocalibration updates
more autocal updates
bug fixes
autocal bug fixes
Final autocalibration updates for release version
pins.h update
Merge pull request #2 from RichCattell/development

Development