Moved VirtualSpatialIndex check into a new mechanism that should allow
us to add further sanity checks in the future.
To test this I've had to commit a binary sample SpatiaLite database to
the repository. I included a build script for creating that database.
Closes#466
Refs #462
* inspect command now just outputs table counts
* test_inspect.py is now only tests for that CLI command
* Updated some relevant documentation
* Removed docs for /-/inspect since that is about to change
I've run the black code formatting tool against everything:
black tests datasette setup.py
I also added a new unit test, in tests/test_black.py, which will fail if the code does not
conform to black's exacting standards.
This unit test only runs on Python 3.6 or higher, because black itself doesn't run on 3.5.