[RFC] Added list node types command and changed n/s of register

So this is an RFC for the list node types command because I'm not sure if we can add anything extra. I have also taken the liberty of moving "register-node-types" to "type:register".

```` bash
$ ./bin/phpcr phpcr:type:list
nt:activity
  Supertypes:
    > mix:referenceable
    > nt:base
nt:address
  Supertypes:
    > nt:base
nt:base
nt:childNodeDefinition
  Supertypes:
[...]
````