Addition of gitreload role for github Web hook course imports

Also support updating repositories such as python graders
from xqwatcher/xserver
Reference edxapp settings for repo directory
Reorder and use deploy.yml tasks
Move gitreload to use gunicorn configuration file
gitreload change log entry added
Merge pull request #1679 from mitodl/cg/gitreload

Addition of gitreload role for github Web hook course imports
Install and use pip-accel for jenkins workers
Workarounds for pip-accel