The schema only uses valid-from and doesn't understand date.
Refs #5422

Avoids an unnecessary incref/decref of the internal PyObject pointer
when it is copied and destroyed.
Refs #8000

and fix the test.
Refs #7019

Note technically related to this ticket but while we're improving tests...
Refs #8000

It had been implemented incorrectly and it looked as if it was passing
when it wasn't.
There was also a bug with the getReferenceFrame import that this also
caught and fixed.
Refs #8000

Now obsolete with the removal of the v1 API. Nothing was looking at it.

re #8001

The new ones are:
* python.plugin.directories
* user.python.plugin.directories

Refs #6875

Warnings have been given for 2 releases. Uses AlgorithmFactory.subscribe
instead.
Refs #6874