Make documentation more future-proof

Ansible roles will be kept in '/ansible/roles/' subdirectory, which
should make them future-proof in case we want to add documentation about
other Ansible-related things or even different configuration management
frameworks.
Lower index depth in Ansible roles
Add documentation for all Ansible roles
Make role index only 1 level deep
Fix .rst errors
Fix header length
Fix more .rst errors in docs
Merge pull request #11 from drybjed/rearrange-roles

Rearrange role documentation