update documentition with license issues for dependancies

[edickie]

We are adding MSM as a dependancy.

Note this from T. Coalson:

Just a reminder: the MSM code/binary is forbidden from commercial use (similar to FSL), because of the terms of the ELC and HOCR discrete optimization libraries. Commercial interests would need to make arrangements with Waseda University (and maybe oxford, as it uses some FSL code, and I am unsure of the details of the FSL commercial restrictions).

I similar situation exists for Freesurfer and FSL.

Will need to add something to the docs about this.