implemented connectors for pyNN.nest backend, adapted projection class accordingly and added NativeRNG class for pyNN.nest backend
Merge https://github.com/NeuralEnsemble/PyNN into commit_nest_connectors

Conflicts:
	src/nest/projections.py
fixed imports in src/nest/connectors.py
fixed layout issues in src/nest/standardmodels/synapses.py
fixed NewConnect -> Connect to adapt to name changes in NEST
removed NEST_SYNAPSE TYPES construction
fixed layout in nest/standardmodels/synapses.py
Update recording.py

Adapted NewConnect -> Connect
Update projections.py

Fixed comment in projection._connect().
inserted type conversion when creating poisson generators with parrot neurons because the new nest Connect function is sensitive to this
Merge branch 'commit_nest_connectors' of github.com:mschmidt87/PyNN into commit_nest_connectors
Merge branch 'commit_nest_connectors'

Conflicts:
	src/nest/__init__.py
	src/nest/connectors.py
	src/nest/projections.py
	src/nest/recording.py