Octopus: Add ability to set and get records by id capability.
The intent with this patch is that only someone possesing a certain id cap
can retrieve records that were stored with this id cap.
To this end, two new functions were added to the client interface of octopus:
* oct_set_with_idcap(struct capref idcap, const char *attributes, ...)
Sets a record using the id capability as the key/name of the record.
* oct_get_with_idcap(char **data, struct capref idcap)
Retrieves a record using the id capability as the key/name.
Note that octopus and the SKB do not support dedicated namespaces atm.
Therefore a record saved with oct_set_with_idcap() could be retrieved by
oct_get().
Moreover, format octopus.if to 80 columns.