Avoiding seeing the name "Tinycontents" in the admin
Make content blocks searchable in the admin
Fail faster if the context variable does not exist

We're always going to fail if this happens - let's just
avoid doing a database query.
Whitespace tidy
Use parser.compile_filter instead of my half-baked attempt
Test this stuff works with {% with %}

Pretty sure with just sets context variables, these tests
are just for completeness.