fix up search representation bugs per issue #13
update samples/spec to cover issues #13 #14 #15

Change title to "Uniform Basis for Exchanging Represenations (UBER)"
Change "Uber" to "UBER" throughout document
Change "diff" to "partial", "update" to "replace"
Change "send-format" to "sending", "receive-format" to "accepting"
In JSON, make "rel", "sending", and "accepting" arrays
Add Normative refs to RFC2616 and RFC5789
Add Informative ref to CoAP-18
several minor editorial fixes
update Acknowledgements
update Acknowledgements
Merge pull request #18 from mamund/spec-fixes

Various fixes for UBER spec covering issues #13, #14, & #15