Django 2 transition

[changeling]

Added on_delete to ForeignKey definitions in models. Using PROTECT at the moment, though it might be worth considering which on_delete is best in each instance.

Removed version dependency from pip ... django ... in setup.sh.

[changeling]

From my limited testing, this seems to be the only barrier to working with django 2.x.

If there are concerns about further testing, perhaps it would be worth creating a django_2_transition branch and I could re-target this PR to that branch.

[briot]

I am ready to merge this one, but there are some conflicts because some of my own changes on HEAD also appear in the modified files, and have been modified since. I think with github you need to do pull requests from a branch (which I find unfortunate, has been a problem for me in other repositories)... Sorry for the inconvenience

[changeling]

This should be clean. I went ahead and reset the branch to your master, then redid the commits.

Oh, on a side note, one thing that may be useful with the more recent Django versions is the index-definition in a model's Meta (makemigrations automatically creates the necessary migration file), as in:

    class Meta:
        """Meta data for the model"""
        ordering = ("date_sort",)
        db_table = "place"
        indexes = [
                models.Index(fields=['id', 'date', 'date_sort', 'parent_place', 'name'], name='place_list-all_idx'),
        ]

I went through the following sequence:

All Places Clicked:
---
Log Entries:
2019-03-14 23:34:56,590 get geneaprove.views.places.PlaceList.get(<JSONViewParams: {}>)
2019-03-14 23:34:56,673 (0.080) SELECT "place"."id", "place"."date", "place"."date_sort", "place"."parent_place_id", "place"."name" FROM "place" ORDER BY "place"."date_sort" ASC; args=()
--
Query:
SELECT
    "place"."id",
    "place"."date",
    "place"."date_sort",
    "place"."parent_place",
    "place"."name"
FROM
    "place"
ORDER BY
    "place"."date_sort"
    ASC;
-
Django Model Meta-defined Index:
    class Meta:
        """Meta data for the model"""
        ordering = ("date_sort",)
        db_table = "place"
        indexes = [
                models.Index(fields=['id', 'date', 'date_sort', 'parent_place', 'name'], name='place_list-all_idx'),
        ]

Django-created Migration SQL:
CREATE INDEX "place_list-all_idx" ON "place" ("id", "date", "date_sort", "parent_place_id", "name");
---

[briot]

Indexes will definitely be useful. They will need careful consideration, of course...

[changeling]

Absolutely. I played with that a couple of others simply to experiment with the process and the migration path. But definitely worth consideration.