ENH add_dig_points, SetChannelMixin, reorganization

This is WIP.

Adds function apply_dig_points to apply hpi, cardinal, and dig points to the Info.

Remove unnecessary import functions for np.loadtxt.

Needs test. Not ready for review
Well it's not independent in that in thinking about what should be exposed, which should not necessarily be the same function that kit2fiff uses internally. When exposing something you need to add a lot of check and options that the internal function does not need. I would make a private and efficient/simple make_dig and find a way to expose the functionality that makes it maximally user friendly.



> On Dec 8, 2014, at 12:04 PM, Teon <notifications@github.com> wrote:
> 
> In mne/io/kit/kit.py:
> 
> >  
> >          if isinstance(elp, string_types):
> > -            elp_points = read_elp(elp)[:8]
> > -            if len(elp) < 8:
> > -                err = ("File %r contains fewer than 8 points; got shape "
> > +            elp_points = read_dig_points(elp)
> > +            if len(elp_points) != 8:
> that was more or less the functionality I started with. I think the function you propose could exist but it is independent of this function. it would be something that would belong to the channels module.
> 
> —
> Reply to this email directly or view it on GitHub.
>