Implement facility to provide out-of-model files as explicitDataBinaryFiles.

[sebjameswml]

This for parameter exploration - it would allow you to provide a weight map generated by some external system (e.g. matlab) in place of the in-model explicitDataBinaryFile.bin file. I need this now so I can experiment with different collicular->LLBN weight maps in the oculomotor model.

[sebjameswml]

The form of the option might be -d "explicitDataBinaryFile11.bin:/full/path/to/alternative.bin"

[ajc158]

This can be done manually through substituting the file before simulation - do we need an interface?

[sebjameswml]

An interface isn't necessary, but I felt it would be convenient. I've been doing this by modifying a copy of the model for each iteration.