Better error handling for capture issues during timelapsing

Should help debugging issue #425 and any future problems in that area.
(cherry picked from commit 1a7a468)
Decrease image counter if an image could not be captured from webcam

Should keep rendering of timelapse from breaking if only a couple of images couldn't be captured due to whatever reason. Suggested by @midopple in #344
(cherry picked from commit bf9d5ef)
Added removal of pyc files (and their parent folders if they are empty after that) to the python setup.py clean command
(cherry picked from commit 9e014eb)
Timelapses: Do not try to use image counter if still set to None and synchronize decrementing of image counter via mutex as well

 Possible fixes for #693, the latter maybe also for #690
Merge branch 'master' into devel

Conflicts:
	setup.py
	src/octoprint/timelapse.py
Only decrement the image counter if it is set and larger than 0

Backported from devel
Merge branch 'master' into devel