Create a feature list page

[aanganes]

We should have a wiki page that lists the features we're currently supporting, as well as somewhat of a roadmap of what features we are planning on supporting (with milestone/time info if possible) and features that we're not planning on implementing (if there are any).

[aanganes]

Page created here: https://github.com/mitreid-connect/OpenID-Connect-Java-Spring-Server/wiki/Features
Needs filling in.

[jricher]

Have filled in some text.