new rule: templates include ansible_managed

[wookietreiber]

The idea is that all files deployed with Ansible contain ansible_managed in one form or another.

• (configurable, as list) check runs on all files in these sub-directories, default: templates
• (configurable, as list) what to look for, e.g. as default {{ ansible_managed }}, {{ ansible_managed | comment }}, {# ansible_managed #}
• this lint should likely be at most warning by default

Note: I've just realized that some formats, e.g. JSON don't have comments. So I've added {# ansible_managed #} as a get out of jail to the list of defaults.