Added names and links to table of RFCs/XEPs.

I found it hard to get value from casually glancing through the Spec Compliance table as I have not memorized all of the RFC/XEP numbers and purposes.  :)  So I added a column for the name of each RFC/XEP and carefully filled them in, using the following as reference:

http://xmpp.org/xmpp-protocols/xmpp-extensions/

I also linked the spec numbers in the first column to the authoritative web page for each for convenience.