Reduce menu and honor services permissions.

I've found distracting to have two very specific menu entries, used for debug (the client also requires devel module to work) so I came over it a change the purpose. Instead of debugging the WSDL file, lets put it near the server configuration, so we can make room to manually set a WSDL later just in case we find problems generating it.

The WSDL view page (still is named debug) has been set as a local task when editing an endpoint, and will onyl be available when the edited endpoint is a soap server. Also the custom access function now honors the services permissions, and checks that user has 'administer services' permission. It could be tricky to require an additional permission just to use Server as an option in the whole services settings section.

Currentl the patch leaves the client debug code useless, but as I described in the readme, reading a user or a node as a fixed debug menu entry is not the way to go. I'd preffer much to write a simpletest case (and I will do) than having this menu enabled in the system for nothing most of the time.

I'm in favor of use the WSDL local task provided by this patch as a 'view' and optionally alter the generated wsdl file than just a simple 'debug' option. Sometimes a manually modified version might provide a quick fix when a SOAP client refuses to work and we have to start coding changes to fix specific cases.

So, in the end, if no debug code is included in the module (and I'd like not to include at all), the readme must be updated.