Fixed #14877 -- repeated deletion using formsets

When a formset contained deletion for an existing instance, and the
instance was already deleted, django threw an exception. A common cause for
this was resubmit of the formset.

Original patch by Trac alias olau.

In addition this commit cleaned some code in _construct_form(). This
was needed as the primary key value the user submitted wasn't converted
correctly to python value in case the primary key field was also a
related field.
Merge pull request #1829 from akaariai/ticket_14877

Fixed #14877 -- repeated deletion using formsets

Reviewed by Loic Bistuer
Add instant autoreload on platforms supporting kqueue.
Reduce the set of events that trigger a reload.

This seems to avoid multiple reloads.
Merge pull request #1830 from aaugustin/instant-reload-os-x

Add instant autoreload on platforms supporting kqueue.

Fix #21356.
Started attackign the next flake8 violation
Fixed #21339 -- Documented removal of some form field error messages
Fixed #15529 -- More permissive geojson syntax in constructor

Thanks Wouter Klein Heerenbrink for the report.
Fixed #18508 -- tests for repeated deletion bug in ModelFormSet

The ticket's issue was already fixed by patch for #14877.