Convenience classes for widget Actions

[corranwebster]

This PR adds:

• some simple field widgets for data entry
• an Action subclass that supports embedding them in toolbars
• an Action subclass that supports embedding TraitsUI views in toolbars

Fixes #349

[codecov-io]

Codecov Report

Merging #360 into master will increase coverage by 1.15%.
The diff coverage is 81.28%.

@@            Coverage Diff             @@
##           master     #360      +/-   ##
==========================================
+ Coverage   35.15%   36.31%   +1.15%     
==========================================
  Files         463      481      +18     
  Lines       25820    26397     +577     
  Branches     3838     3909      +71     
==========================================
+ Hits         9076     9585     +509     
- Misses      16350    16399      +49     
- Partials      394      413      +19

Impacted Files	Coverage Δ
pyface/action/api.py	100% <100%> (ø)	⬆️
pyface/action/traitsui_widget_action.py	100% <100%> (ø)
pyface/fields/combo_field.py	100% <100%> (ø)
pyface/fields/spin_field.py	100% <100%> (ø)
pyface/fields/api.py	100% <100%> (ø)
pyface/fields/text_field.py	100% <100%> (ø)
pyface/ui/qt4/fields/spin_field.py	100% <100%> (ø)
pyface/ui/wx/fields/spin_field.py	100% <100%> (ø)
pyface/ui/qt4/fields/field.py	68% <68%> (ø)
pyface/fields/i_text_field.py	71.01% <71.01%> (ø)
... and 41 more

---

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[jwiggins]

I'm basically 👍 on this. Just adding a few remaining comments now that I've done a more careful reading.

[corranwebster]

I'm starting to write tests and finding some interesting issues, so there are likely to be some updates on this (currently SpinField is behaving oddly in tests).

[corranwebster]

This is being delayed a bit more: dispatch of traits listeners needs to be on the UI thread so I need to refactor away from _*_changed forms :(

[corranwebster]

... except UI dispatch requires TraitsUI to be imported, which means tests have errors unless there happens to have been an import of TraitsUI somewhere.

I am knee-deep in yak hair right now.

[corranwebster]

@jwiggins This has been thoroughly worked over, so a re-review would be appreciated at some point.

[jwiggins]

Found a few things looking over the most recent changes. I'm about to do another pass over everything...

[jwiggins]

It's good that this is covered by tests now. I won't push too hard for big changes, because I'd rather see this merged soon.

That said, the repetition in the testing code is a bit of a smell. It would be nice to track that in a separate issue and clean it up later. (I see that GuiTestAssistant only exists for Qt...)

[corranwebster]

I think the testing of the field classes is about as tight as you are going to be able to get it, although it would be nice to have the GuiTestAssistant available to make some of the event processing nicer and a bit more robust. The action testing is not as good, but it should really be done as part of re-writing the tests for all the actions.

[jwiggins]

Pending a clean CI run, this is good-to-go

[corranwebster]

Looks good. Merging.