[keycloak-dev] Hacking on Keycloak docs

[Stian Thorgersen]

I've updated the main README.md in the GitHub repo to include some details on how to build and run Keycloak.

As we had some developer related docs in GitHub wiki (https://github.com/keycloak/keycloak/wiki) and some in repo itself (https://github.com/keycloak/keycloak/tree/master/misc) I've deleted the out of date stuff and moved everything to https://github.com/keycloak/keycloak/tree/master/misc.

I've also added a Hacking on Keycloak guide (https://github.com/keycloak/keycloak/blob/master/misc/HackingOnKeycloak.md).