Correct the maximum DID length defined in "serval_types.h" from 32 to
31. Add a definition of the maximum identity Name length and use it
instead of the bare constant 64, eg, in the MDP_DNALOOKUP request
handling code.
Introduce a dataformats.h function for validating an identity name, and
use it to validate the 'name' parameter in the CLI 'keyring set'
command.
Add 'did' and 'name' parameter validation to the GET /restful/keyring/add
and GET /restful/keyring/SID/set requests (#131).
Rename keyring_set_did() to keyring_set_did_name() and assert that DID
and Name lengths have been validated before storing in the keyring.
Update the Keyring REST API tech document.
