include custom widget

[luiztauffer]

This allows user-created widgets to be included in the neurodata_vis_spec, can be used like this:

import pynwb
from pynwb import NWBFile, NWBHDF5IO
from nwbwidgets import nwb2widget
from mywidgets import TunningCurvesWidget,

io = NWBHDF5IO('file.nwb', 'r')
nwbfile = io.read()

# include custom widgets
include_widgets = [{
    'widget': TunningCurvesWidget,
    'label': 'Tuning Curve',
    'pynwb_class': pynwb.misc.Units
}]

nwb2widget(node=nwbfile, include_widgets=include_widgets)

For now it only works for items which are OrderedDict. Maybe we would like to extend most items to be OrderedDict? This would in principle just nest each item in a single Tab, but allows for the possibility of easily adding customized widgets

[codecov]

Codecov Report

❌ Patch coverage is 37.50000% with 10 lines in your changes missing coverage. Please review.
✅ Project coverage is 68.91%. Comparing base (616ed9a) to head (43bb21e).
⚠️ Report is 164 commits behind head on master.

Files with missing lines	Patch %	Lines
nwbwidgets/view.py	37.50%	10 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #149      +/-   ##
==========================================
- Coverage   69.15%   68.91%   -0.25%     
==========================================
  Files          30       30              
  Lines        2169     2184      +15     
==========================================
+ Hits         1500     1505       +5     
- Misses        669      679      +10     

Flag	Coverage Δ
unittests	68.91% <37.50%> (-0.25%)	⬇️

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[bendichter]

@luiztauffer see edits to my comment. You may have to test it a bit. I'm not 100% sure it will work as I wrote it

[bendichter]

Now that I am thinking about it, maybe the values of neurodata_vis_spec should always be OrderedDicts, and we would only present it as lazy_tabs when the length is > 1. What do you think?

[luiztauffer]

@bendichter I agree, at least with most of the items. It makes adding custom widgets easy