This commit does a lot of the work of refactoring the access table in a table with id's instead of strings.

The result does compile, but has not been tested. It may eat your kittens.

It is now possible to input ssh keys in a number of formats: openssh, SSH2 or just the base64 encoded key.

All basics are implemented. Missing are the right (localized) strings
and the page markup could have a look at by a frontend guy.

Conflicts:
	modules/setting/setting.go

Conflicts:
	templates/repo/release/list.tmpl
	templates/user/dashboard/dashboard.tmpl

Conflicts:
	routers/repo/setting.go

Fixes issue #370: https://github.com/gogits/gogs/issues/370

Removes the limitation to RSA and enables us to use all key types
SSH recognizes.