Added GPG verification

* Added new files for key pull and verification
* Dockerbot now enforces GPG when testing PRs but NOT when
  doing branches
Merge pull request #1260 from psav/dockerbot_gpg

Added GPG verification
Added provisioning inside check_pr
Fixed bug in setup.sh
Merge pull request #1263 from psav/fix_setup_sh

Fixed bug in setup.sh
Merge pull request #1262 from psav/checkpr_provision

Added provisioning inside check_pr
Provision after key checking
Merge pull request #1264 from psav/fix_setup_sh

Provision after key checking