Add vhost config file extension for RedHat-based distributions

Default Apache installations on CentOS/RedHat will only load files ending in .conf, but the vhost config files are created without any extension.

I've added a 'confext' parameter to the map, and use that when defining the vhost config files. I'm not sure what the appropriate behavior is on FreeBSD, and I don't believe it's needed for Debian, so both of those have their confext set to an empty string, so that should preserve their existing behavior.