ome major changes:
1) dynamically allocated arrays are now copied into placeholder pointers on the device named dd_* which removes the necessity of passing in the pointers into the kernels all the time
2) added support for continuous dynamics of synapse variables.
... other minor changes and bug fixes.
Merge branch 'development' of https://github.com/genn-team/genn into development

Conflicts:
	lib/src/generateCPU.cc
	lib/src/generateKernels.cc
	lib/src/generateRunner.cc
	userproject/MBody_userdef_project/model/GNUmakefile
	userproject/MBody_userdef_project/model/MBody_userdef.cc
	userproject/MBody_userdef_project/model/classol_sim.cu
	userproject/MBody_userdef_project/model/classol_sim.h
	userproject/MBody_userdef_project/model/map_classol.cc
	userproject/MBody_userdef_project/model/map_classol.h

All conflicts resolved by inspection.