data_cast as numpy dtype

[djps]

Describe the bug Makes sense to refactor parts of simulation_options so that the data_cast option is a numpy type rather than a string

[waltsims]

@djps can you better describe what the current behavior is and what enhancement is needed?

[djps]

In simulation_options the argument data_cast is either either off, single or double.

I think setting a default as np.float64 with another accepted option being np.float32.

[waltsims]

Currently in save_h5_file all values are cast to float32 here. We can continue to look into this behavior and try to ensure that precision is taken into account.

[djps]

Seems to replicate the matlab behaviour in writeMatrix