Merge pull request #1 from illuminarti/Fix_E_Speed

Fix step rate bug (especially for retraction)
Patch in Leapfrog changes
Merge remote-tracking branch 'upstream/Marlin_v1' into Marlin_v1

* upstream/Marlin_v1:
  Merge pull request #1 from illuminarti/Fix_E_Speed
Merge branch 'Marlin_v1' into Creatr

* Marlin_v1:
  Merge pull request #1 from illuminarti/Fix_E_Speed