Also, check config before applying

First implementation of TOFS for:
nginx_config, passenger_config, servers_config and snippets
Introduced tplroot on modified files as well
Fixed GH link of nginx.conf file in docs/TOFS_pattern.rst
Fixed test for snippets name pillar

BREAKING CHANGE: all previous `nginx` based configurations must be reviewed;
`nginx.ng` usage must be promoted to `nginx` and any uses of the original
`nginx` will have to be converted.

Build NGINX from source with nginx.ng state with support for passing
compile time flags necessary for installing modules such as more headers
by the openresty project.