hydra-evaluator improvements

* The "Jobset" page now shows when evaluations are in progress (rather
  than just pending).

* Restored the ability to do a single evaluation from the command line
  by doing "hydra-evaluator <project> <jobset>".

* Fix some consistency issues between jobset status in PostgreSQL and
  in hydra-evaluator. In particular, "lastCheckedTime" was never
  updated internally.

src/sql/hydra.sql

@@ -69,6 +69,7 @@ create table Jobsets (
     schedulingShares integer not null default 100,
     fetchErrorMsg text,
     forceEval     boolean,
+    startTime     integer, -- if jobset is currently running
     check (schedulingShares > 0),
     primary key   (project, name),
     foreign key   (project) references Projects(name) on delete cascade on update cascade