BUGFIX: cluster direction reconstruction

There was a bug resulting in identical cluster direction reconstructions.
Irrespective of the stations that were selected to reconstruct the
direction, the same set of stations was used in the actual calculation.
Bugfix: check for partial duplicate coincidences

Previous behavior::

    >>> c._do_search_coincidences([(u,) for u in range(10)], 5)
    [[0, 1, 2, 3, 4],
     [1, 2, 3, 4, 5],
     [2, 3, 4, 5, 6],
     [3, 4, 5, 6, 7],
     [4, 5, 6, 7, 8],
     [5, 6, 7, 8, 9],
     [6, 7, 8, 9],
     [7, 8, 9],
     [8, 9]]

Please note that the final three coincidences are all part of the [5, 6, 7, 8,
9] coincidence.  New behavior::

    >>> c._do_search_coincidences([(u,) for u in range(10)], 5)
    [[0, 1, 2, 3, 4],
     [1, 2, 3, 4, 5],
     [2, 3, 4, 5, 6],
     [3, 4, 5, 6, 7],
     [4, 5, 6, 7, 8],
     [5, 6, 7, 8, 9]]

Only unique coincidences will be stored.  In this unrealistic test, there
are coincidences which are partially identical.  If this really happens in
real life, it is up to the user to identify this.
Inherit overwrite attribute in Coincidence methods
CoreReconstruction: removed N >= 2 requirement

This was necessary in the simulations, but causes trouble in actual data.
Fixed cluster CoreReconstruction

CoreReconstruction now works correctly for a cluster of stations.  It
iterates over the coincidences table and reconstructs the core position
for N >= 3.  The results are stored similarly to the results of the
ClusterDirectionReconstruction table.
Merge branch 'core_reconstruction'
Remove /django/ from url
Flush data file from time to time
Publicdb: reraise exception if uncatched
Coincidences: optionally store cluster instance in results
Allow for easier subclassing of Coincidences
Tutorial: there was no data in example
Tutorial: import sapphire.time_util
FIX: particle arrival times now use baseline

The particle arrival time code used the first 100 samples of the trace to
determine the baseline.  These samples are cut off by the 'reduce data'
feature in the LabVIEW DAQ.  The implementation of 'reduce 'data' is
faulty since it should leave 100 samples intact before the start of the
trace.  The new code uses the baseline as determined by the DAQ and does
not use the first 100 samples.  Closes #3.
Merge branch 'fixtimings'
BUGFIX: data corruption in core reconstruction

CoreReconstruction matched the wrong station to an event in actual data.
In simulated data, this used to be correct since station_id is 1-based in
the simulation, whereas it is 0-based in everything else (see bug #4).
Core reconstruction now uses station averaged signals

This should be configurable.
Fixed PlotCoreReconstruction for cluster Science Park
Merge branch 'master' into tutorial
Removed baggage from coincidences code