Coefficient file parameter checking

[The9Cat]

Summary

The user can append coefficients to an existing HDF5 coefficient file with different parameters than those in the file, leading to inconsistency.

Possible fixes

1. Do nothing; let the user do this.
2. Let the user do this, but skip inconsistent stanzas on read.
3. Update the ExtendH5Coefs to read the header and abort if the basis parameters are different. E.g. nmax, lmax or nmax specifically. Abort if inconsistent.
4. As above, but warn if inconsistent.

Note

Options 3 and 4 will require reading some attributes from the open file but should be an unnoticeable computational hit.