Allow DistanceDependentProbabilityConnector.d_expression to be a
'callable' object as well as a constant or string-based expression
added configure sources to Projection class (not sure if this is the way
to go yet)
Adde CloneConnector to standard connectors for all supported simulators
implemented index based connector class and extended MapConnector to
also be able to use index based functions to determine attributes
Implemented DisplacementDependentProbabilityConnector as proof of
concept of new IndexBasedProbabilityConnector
Tidied up the IndexBasedExpression and moved it outside of the
DisplacementDependentProbabilityConnector class (Expressions should
probably reside in their own modules I expect)
Merge branch 'index_based_connector' into two_sided_synapses
Added gap junction implemented (not fully working)
Gap junctions look like they should be set right from the log file but
the 'vgap' pointer is not to the remote voltage
Added the final missing ingredient (which catches you out every time) by
adding the parallel_context.setup_transfer()
Added some more comments explaining the gap junction implementation
removed stray whitespace that was accidently added
Cleaned up my changes (whitespaces and so forth) to reflect only genuine
changes from master branch
cleaned up filter of non-NaN post-synaptic indices in
_configure_presynaptic
Merge branch 'master' of https://github.com/NeuralEnsemble/PyNN

Conflicts:
	src/nest/connectors.py
	src/neuron/connectors.py
Merge branch 'master' into index_based_connector
Merge branch 'master' into presynaptic_components

Conflicts:
	src/common/projections.py
rewrote neuron.Projection._configure_presynaptic method to use
get(format='list') instead of get(format='array'), which is only fully
returned on the master node
Got gap junctions to work over MPI for NEURON by using (and extending
slightly) the new gather functionality in common.Projection.get
added squeeze to in1d array call in configure_presynaptic