Improve the autohelp scripts

wrapper:
- Don't modify the openstack-manuals repo if it exists, keep it as is
  git wise (no branch change, no pull)
- Install oslo.i18n and hplefthandclient
- First setup the environment, then do the update/docbook work

autohelp.py:
- Handle projects not using oslo.i18n (mostly for havana)

diff_branches.py:
- Update the output format
- Setup the venv for the requested projects only

Change-Id: I48c45a56f4b7b7298fef0b7595d62e445c92df39