Improving the sandbox update script

This modifies the edx_ansible role to dump a clean var
file on disk that can be used for subsequent update runs
so that config vars will not be lost

also changes the ansible tmp directory to /var/tmp which is a better
location than using $HOME (used for debugging mostly)
install the complete edx_ansible role
Merge remote-tracking branch 'origin' into jarv/dump_vars
adding the missing dumpall.yml.j2 file
removing remote_tmp override
adding ease and certs to version removal
Merge pull request #640 from edx/jarv/dump_vars

Improving the sandbox update script