Rename new checksetup manage command

[Russell Keith-Magee]

In commit ​91f317c7 Daniel committed a new management command called "checksetup" to perform warning-level checks for problems that may occur on upgrading between versions.

There is some overlap here between this new feature, and the scope of the 2013 GSoC project to refactor the "validate" command. One of the aims of this project is to reduce the naming collisions around "validate" -- it could refer to "form validation", "model validation" or "field validation", depending on how it's used.

This GSoC project will also involve the introduction of a new management command as part of reducing this naming collision; one of the candidate names was "check"

Before 1.6 is finalized, we should rename checksetup so it can be used as a generic command for all checks, rather than just the single-purpose check it's currently performing.

[Russell Keith-Magee]

​Mailing list discussion here

[Russell Keith-Magee]

Consensus on mailing list seems to be that "check" is the best name; I've got a commit for this that will land shortly.

[Russell Keith-Magee]

Trac triggers seem to be busted; this was committed in ​03465639

[Collin Anderson]

checksetup is still in the django-admin docs
​https://github.com/django/django/blob/master/docs/ref/django-admin.txt#L92

​https://github.com/django/django/pull/1353

(i figure this is small enough to not warrant a new ticket number.)

[Tim Graham <timograham@…>]

In a7d97a6778ca528199920901ed2f66e289ee5a44:

Fixed #20653 -- Renamed checksetup -> check missed in [03465639]

Thanks CollinAnderson for the report.

[Tim Graham <timograham@…>]

In b30a872973b6903e52d93532175d60d3bf68f888:

[1.6.x] Fixed #20653 -- Renamed checksetup -> check missed in [03465639]

Thanks CollinAnderson for the report.

Backport of a7d97a6778 from master