add tests for three requirements not covered

Make sure we have test coverage for the following three requirements:

* 4.2.4.2 LDP servers SHOULD allow clients to update resources without requiring detailed knowledge of server-specific constraints. This is a consequence of the requirement to enable simple creation and modification of LDPRs.

* 4.2.8.2 LDP servers MUST indicate their support for HTTP Methods by responding to a HTTP OPTIONS request on the LDPR’s URL with the HTTP Method tokens in the HTTP response header Allow.

* 4.3.1.3 The representation of a LDP-RS MAY have an rdf:type of ldp:RDFSource for Linked Data Platform RDF Source.