sbin/hammer: Expand hammer show directive to lo:objid:rectype:key:tid

sbin/hammer: Expand hammer show directive to lo:objid:rectype:key:tid

- Make hammer show command take rectype:key:tid as an optional part
  of the search directive in addition to the existing part lo:objid.

- Unspecified fields are handled as wildcard.

- rectype:key:tid all have lower priority than existing lo:objid
  (in actual filesystem's btree implementation) so these new fields
  give hammer show command extra conditions on btree search given
  that higher priority fields lo:objid do match.