Fixed #25274 --- Made inspectdb handle renamed fields in unique_together.

[jbzdak]

Inspectdb now handles renamed fields in unique_together.

It was tested on sqlite and postgresql (I don't know whether I'm supposed to check it on other all databases).

[charettes]

Add a trailing comma.

[jbzdak]

I have added suggested changes, two questions:

1. Should I squash those two commits
2. After browsing code for second time I'm wondering if tests could be done better. Here is the issue: Tests implicitly test for the order of unique_togetgher entries so if two columns were present in unique_together in reverse order ("foo", "bar") instead of ("bar", "foo") this would be unittest error, while at the database level these two constraints are equivalent (as far as I know). I could amend tests to fix this behaviour, but it sould decrease test clarity. Is this worthwhile?

[timgraham]

Splitting up the test into a class didn't seem to add clarity, so I moved it back into a method. I didn't look closely about the issue with field name ordering, but I haven't seen the test failure non-deterministically so I think we're okay for now. Merged in 2cb50f9, thanks!