Merge pull request #512 from antaflos/no_trailing_slash_proxypass

No trailing slash for ProxyPass/ProxyPassReverse
Make LogLevel configurable for vhost

Add a `loglevel` parameter, which defaults to `undef`, in
`apache::vhost` to allow overriding the global server configuration's
log level (warn) on a per-vhost basis. Includes updated documentation
and basic spec tests. Fixes issue #510.