Add OpenMP support to standalone mode, including the spike queue
Default to OpenMP with 1 thread, using 0 threads does not work in SynapticPathway etc.
Thanks to Marcel, turned synapses.h and network.cpp into templates, such that we can use a function (openmp_pragma) that will handle
the insert of pragma statements in the code. Now the number of threads can be given as a brian preference. By default, if 0, nothing is done and
the code is not relying on openmp at all. Otherwise, if a positive number is given, then that number of threads is used
Forgot one file. Now I'll try to merge that openmp branch with latest master before launching a pull request
Remove files that are not needed anymore because they have been turned into templates now
Merge branch 'openmp' with 'master'. Fix few things related to the report system, needs some tests to check that openmp support is
fine, and I'll push it

Conflicts:
	brian2/devices/cpp_standalone/brianlib/network.cpp
	brian2/devices/cpp_standalone/brianlib/network.h
	brian2/devices/cpp_standalone/device.py
	brian2/devices/cpp_standalone/templates/main.cpp
	brian2/devices/cpp_standalone/templates/ratemonitor.cpp
Fixa bug in the summed variable synapses, that occured during the merging, and change the default value of the
openmp preference to 0. Everything seems to run smoothly, speedup depends on the simulation, so more intensive
benchmarks should be performed