Support all families

[danielward27]

Many families currently just raise a not implemented error. It would be ideal to have at least a single testcase for each family too.

[danielward27]

Mostly done except for a few more specialised families in https://github.com/danielward27/pymgcv/pull/52.

The unsupported families, are listed at the bottom of families.py, currently raising NotImplementedErrors.