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.
Should we mention that "an error will be raised if the file is not valid"?