Makes the min number of connections for binary writing into a preprocessor parameter.
Code tidying, in advance of figuring out how connection files can keep their names.
Implements reliable connection.bin file naming - this commit by Alex C
Some work in progress - removing use of the export_to_binary setting
Now SpineCreator no longer exports for simulation - it just saves the project in the model dir and uses the -e option for convert_script_s2b
Notes about next thing to do
Merge branch 'model_expansion_code' of github.com:SpineML/SpineCreator into model_expansion_code

Conflicts:
	connection.cpp