Add M221 to M503/M502

[ThomasToka]

• add M221 to output of M503
• reset value on M502 to DEFAULT_EXTRUDER_FLOWRATE stored in configuration_adv.h

Description

Add M221 to the Output of M503 and reset on M502 to a value stored in configuration_adv.h

Requirements

none

Benefits

See value of M221 in M503

Configurations

inside PR. One variable to add

Related Issues

Todo:

• cover multiple extruders if present on reset, report
• cover multiple extruders if present and needed with M501
• reset DEFAULT_EXTRUDER_FLOWRATE for all extruders if present to value stored in configuration_adv.h

[thinkyhead]

The Flow Percentage is the sort of setting that probably should be reset to 100% on every reset, because if the E flow percentage is altered at any point or for any reason and then this is followed by M500 it can cause a lot of confusion for subsequent print jobs. This print parameter is especially troublesome because most slicers don't bother to send M221 S100 as part of their standard precursor. It is generally best to have the flow at the start of any print be 100% (when not overridden in the slicer) as this is what is expected, and then users adjust it up or down as needed from there. It would be an easy prank for someone in a shared workshop or school situation to set the flow percentage to some very high or very low value and save it to EEPROM to mess with the next unsuspecting user, causing them to waste time and material trying to figure out why their print keeps coming out badly. It would probably be common for users to accidentally prank themselves this way too.