Support for new Bootstrap4 alpha5 markup

[darklow]

I haven't checked 100% all bootstrap markup yet, but 4x main changes I mentioned in my issue #658 post are ready. Let's me know what you think. We can also discuss checkbox double label issue before closing PR.

[codecov-io]

Current coverage is 95.28% (diff: 93.47%)

Merging #660 into dev will increase coverage by 0.01%

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[darklow]

I do not feel confident of this conditional check that I needed to add to few templates:

<div class="form-group{% if not form_class or 'form-inline' not in form_class %} row{% endif %}">

Thing is - for inline forms we need just .form-group class, but for non-inline forms we need to use it together with .row and currently only difference is in form_class variable. Let me know if you want me to add template filter maybe or even global context variable {{ has_inline_class }}?

form-group {%if form_class|has_inline_class %}...

[darklow]

I will add some more markup updates in nearest time, do not accept PR yet.

[zoidyzoidzoid]

@darklow Thanks for this PR. I'll take a look at it this week.

[auvipy]

alphha6 is released http://blog.getbootstrap.com/2017/01/06/bootstrap-4-alpha-6/ next is beta1 could you update the pr with that?

[carltongibson]

@darklow Any chance you could update this to latest dev? Thanks!

[carltongibson]

Also, can you look at #676? — it's only a one liner so could easily be handled here. (Maybe it already is?)

Thanks.

[darklow]

I think we should wait BS4 final, it just too much refactoring on each new alpha. In the meanwhile feel free to copy edited templates from this PR to your own template directory and adjust if needed.

[zoidyzoidzoid]

Definitely a bunch of work to keep up with bootstrap v4 alpha/beta. And now there are conflicts. Hopefully will get to take a look at this properly in the next month or two.

[carltongibson]

See #732: I've asked for help finalising Bootstrap 4 support, and we'll do a new release in the autumn before Django 2.0, or sooner if we get lots of input.

BS4 is now "Beta" and should be stable enough. If this PR can be updated for that we'd be glad to have it! Ta!

[zoidyzoidzoid]

I've put these changes into my PR: #735