Allow UI from subdir

[mrdrmmn]

Attempting to use proxypass to place the ui at /ui or anything outside of / results in images being broken. While I could likely work around this, it would be preferable I could relocate it cleanly like the api and checksync.

The primary reason for doing this would to make it easier to have an all in one test environment with graphite under the same vhost. Unfortuately graphite cannot be relocated out of / cleanly either so for now I have graphite running in a separate vhost on a different port. It works, but would be nicer if it could all reside under a single vhost.

[halcyonardency]

Agreed. This should be compatible with any ProxyPass regular setup, including where everything is located under a subdir.