RAPI documentation: Add link targets

A newly added table of RAPI access permissions will link to all
resources and their supported methods. For this reason link targets need
to be added.

The GET method on “/2/nodes/[node_name]” was not separately mentioned.
This is also fixed.

Signed-off-by: Michael Hanselmann <hansmi@google.com>
Reviewed-by: Guido Trotter <ultrotter@google.com>