SLB Alpha Firmware B5.0.3

• Updated defaults spindle selection and order
• Updated default action button behaviors
• Updated default switchbank behaviors
• Addressed LED latching issue
• Applied fix for probe equality checking grblHAL/core#470
• Merged submodule and SL PRs for default settings.
• Increased LED brightness
• Set rotational axis bitmask default
• Reversed order of Aux outputs in board map file