Encrypted passwords and new hosts file for dev capture agents

Created by: si202cam

To avoid having any passwords in clear that might be accidentally deployed, this PR moves passwords from groups_vars/all to group_vars/dev and encrypts them.

The dev-hosts.yml file includes a new entry for a 'dev' group (at the bottom), that inherits all the other capture agents defined in the file, this should result in the groups_vars/dev file being included.

Part of #36 (closed)