Fixed a comment in the planner
Merge pull request #946 from Jnesselr/jnesselr/plannerdoc

Fixed a comment in the planner
Add switch unused feeder(s) off

Having the non-active feeder motors powered on all the time is not
necessary. A feature to deactivate the unused feeder motors has been
implemented. The feature is enabled on default but can be switched off
in the configuration.
renaming the disable inactive extruder feature
Merge pull request #947 from Dim3nsioneer/Marlin_v1

Add feature 'switch unused feeder(s) off'
M30 response is missing linefeed, "ok" therefore not on own line

This leads to the command not being acknowledged properly
by the firmware, leading to consecutive issues in host software
waiting for an acknowledgement.
Merge pull request #949 from foosel/fix/M30_clearToSend_bug

M30 response is missing linefeed, "ok" therefore not on own line