Further bugfixes when using CustomMethod for Head method

After updating to ServiceStack.Common 3.9.33 for the bugfix discussed below on StackOverflow, I was able to proceed further into issuing the HEAD request than before.  Not too much further as I quickly discovered the client attempting to open the request body stream which throws a ProtocolViolationException for HEAD requests (even if you have nothing to write).



[Issuing HEAD request with IRestClient in ServiceStack](http://stackoverflow.com/questions/14059085/issuing-head-request-with-irestclient-in-servicestack/14063619#14063619)

The HEAD verb needed to be added to several conditional checks in various files for enabling use of  query string and to prevent the use of the request body.  These changes were enough to resolve the issue with CustomMethod in a desktop application on Windows 7.  

For convenience, I added two Head overloads to IRestClient which I probably should have committed separately (git newb) but are easy enough to remove if you wish to keep them out.  

Forgot to use a topic branch here (see above) so I will refrain from pushing any further changes pending the outcome of this pull request.

Please let me know if there's anything I can do to assist with implementing these changes.  Thanks!