Add defined type for handling custom configs

Initially I was looking to handle custom configs by creating a temporary
file, validating that file, and creating a file under apache's
`$confd_dir` only if that validation passed. Ubuntu caused issues for me
though, and apachectl was unable to validate config files under
non-default paths. Thus, I ended up with a file resource and two execs,
to remove the config if invalid, and notify the httpd service if valid.

There were some bugs with existing acceptance tests, so fixed those too.