devstack vagrantfile: mount "themes" from host

This mounts the "themes" directory on the host.  This will enable people
who have configured "stanford-style" themes to check out their themes on
the host and have it useable in the devstack.

Two things are a bit odd about this that are worth highlighting.

1. For people not using Stanford-style theming, which are most
   developers and certainly everyone at edX.org, this is a wasted
   export.  It doesn't do any harm, but would it be confusing?  I
   think that's OK.

2. The provision steps checks out the other repos that you need
   (edx-platform, cs_comment_service, etc.).  We're not checking out
   the theme repo ourselves here, counting on the user to do so
   yourself later.  I know this isn't consistent, but I couldn't
   plumb through the theming stuff into the rest of devstack
   provision, at least not right now.
Use vagrant-vbguest plugin to sync VirtualBox Guest Editions versions

Wiki will need to be updated to reflect this addition

Added script to auto install vagrant-vbguest if it's needed
Make LC_ALL default to 'en_US.UTF-8'.

The LC_ALL environment variable is set to en_US in /etc/default/locale
in the precise32 vagrant box, see:

https://github.com/mitchellh/vagrant/issues/1188

When running the python unit tests in the devstack machine, several of the
tests fail with a UnicodeEncodeError when trying to create folders with names
that contain non-ascii characters.

Explicitly setting LC_ALL to en_US.UTF-8 before running the tests fixes this issue,
but it would be nice if the box was set up with the en_US.UTF-8 locale by default.
squashing commits

devstack to not use pre_supervisor

typo error

Taking out edxapp_pypi_local_mirror, replacing with COMMON_PYPI_MIRROR_URL

Adding back - for white space

Conflicts:
	playbooks/roles/edxapp/tasks/deploy.yml
using hosts all for commoncluster
Build from release instead of master
taking out paver task for now
Merge pull request #971 from edx/han/devpi

Using PyPi URL instead of DevPi
typo, forgot to add release
Merge pull request #972 from edx/jarv/change-host-specifiers

using hosts all for commoncluster
Merge pull request #973 from edx/han/vagrant_script

Build from release instead of master
Merge pull request #968 from mtyaka/lc-all-utf8

Make LC_ALL default to 'en_US.UTF-8'.
adding xqueue to commoncluster and warning about reboot
Merge pull request #976 from edx/jarv/add-xqueue-to-common-cluster

adding xqueue to commoncluster and warning about reboot
Use COMMON_PYPI_MIRROR_URL in discern,ora,edx_ansible,supervisor,xqueue,xserver

Make it easier to use a local pypi mirror in the roles listed above
Add my name to AUTHORS, Wang Peifeng <pku9104038@hotmail.com>
Merge pull request #977 from edx/feanil/local_pypi

Feanil/local pypi
Don't use common_pypi mirror for devpi.
Merge pull request #978 from edx/feanil/local_pypi

Don't use common_pypi mirror for devpi.
Removing auto install script