New run_sanity_checks mechanism, for SpatiLite

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

tests/test_cli.py

@@ -0,0 +1,40 @@
+from .fixtures import app_client
+from datasette.cli import cli
+from click.testing import CliRunner
+import pathlib
+import json
+
+
+def test_inspect_cli(app_client):
+    runner = CliRunner()
+    result = runner.invoke(cli, ["inspect", "fixtures.db"])
+    data = json.loads(result.output)
+    assert ["fixtures"] == list(data.keys())
+    database = data["fixtures"]
+    assert "fixtures.db" == database["file"]
+    assert isinstance(database["hash"], str)
+    assert 64 == len(database["hash"])
+    for table_name, expected_count in {
+        "Table With Space In Name": 0,
+        "facetable": 15,
+    }.items():
+        assert expected_count == database["tables"][table_name]["count"]
+
+
+def test_inspect_cli_writes_to_file(app_client):
+    runner = CliRunner()
+    result = runner.invoke(
+        cli, ["inspect", "fixtures.db", "--inspect-file", "foo.json"]
+    )
+    assert 0 == result.exit_code, result.output
+    data = json.load(open("foo.json"))
+    assert ["fixtures"] == list(data.keys())
+
+
+def test_spatialite_error_if_attempt_to_open_spatialite():
+    runner = CliRunner()
+    result = runner.invoke(
+        cli, ["serve", str(pathlib.Path(__file__).parent / "spatialite.db")]
+    )
+    assert result.exit_code != 0
+    assert "trying to load a SpatiaLite database" in result.output