- Batches now have optional "expire time".
  If this time passes and the batch is not retired, abort and retire it.
- Add script "expire_batches" which enforces the above.
  Run it as a periodic task.
- Add a web RPC for setting the expire time of a batch
  (it can be changed multiple times)
- Add a C++ interface for this RPC
- Add a BOINC_SET_LEASE command to the BOINC GAHP
  ("lease" is Condor term for expire time)

Conflicts:
	android/BOINC/src/edu/berkeley/boinc/ProjectsActivity.java
	android/BOINC/src/edu/berkeley/boinc/adapter/ProjectsListAdapter.java

Client (Android): add device_name field to DEVICE_STATUS, so that GUI can tell client the device name