Properly enable serial logging on startup if configured
(cherry picked from commit 2261ddf)
Only match "rs"/"resend" on the start of a line, otherwise the wrong lines might be interpreted as resend requests
(cherry picked from commit ae09a50)
Check if self._comm is None before trying to select a file...
(cherry picked from commit 5631a45)
Added .gco to supported extensions
(cherry picked from commit d51aa65)
Properly handle failed uploads: display message, reset upload status
(cherry picked from commit ce7ccc1)
Merge branch 'devel'

Conflicts:
	octoprint/static/js/ui.js
	octoprint/util/comm.py
Fixed SD upload (managed to break this by introducing temperature offsets).

Closes #249