Domain directory

Helper module for Domain Access which allows example.com/foo to emulate foo.example.com.

Here's the plan:

-- Allow each domain record to be registered with one or more 'folder' or 'path' matches.
-- On hook_domain_bootstrap_full(), load the domain (if any), corresponding to the inbound path.
-- Either a) issue a redirect to the proper subdomain or b) use hook_url_inbound_alter() to hide the path directive as necessary. (This should be configurable.)
-- Use hook_domainload() to alter the path element of the domain, if necessary.