Support compressed requests

Sometimes POSTs can get quite big and it would be beneficial for REST clients (especially on mobile devices) if the server supported gzipped requests in addition to responses.

We need to modify GZIPFilter to wrap the request in a way that unzips the body if the "Content-Encoding: gzip" header is set.

In order to test you need to enable gzip going to System Administration -> Settings -> gzip.enabled set to True (restart of the server is required).

Please add "gzip.acceptCompressedRequestsForPaths" global property with a list of comma-separated regular expressions to match on URLs (do not require to enter the first part of the URL with protocol, host, port and context path, which you can get with getServletContext().getContextPath(), default to none i.e. empty value "").

Also the server should respond with 415 (Unsupported Media Type) if the feature is disabled entirely or for the given path.