Document that you can set the installation path to `false` in order to
serve the web UI in-place, i.e. without copying it to some publicly
served folder.

This treated only the root (typically '/clockwork') as part of
the web UI. Now, it treats that and everything inside that dir
as parts of the web UI.

In particular, you can now send a 'Content-type' header, so that
this can be used to serve any type of file in the response.

This used to only serve the root HTML doc as container for the iframe with
the actual app. Now, it treats anything under the root path (typically
'/clockwork') as a web asset and serves it accordingly.

…moved "uri" setting, code tweaks.