Working version of generic plugin + basic tests

The generic plugin, called ubuquitous in honour of Ubiquity Press who
suggested it and had a Creative Commons-recommended license statement on
their journal pages, has all the license statements we're aware of as of
now.

The tests included with this commit simply test 2 of those license
statements - there's no point in testing all of them since they (or more
specific versions) are already tested by other plugin tests. The new
Ubiquity Press license statement is included though.

However, there are no workflow tests included - does the generic plugin
activate when it should, does it break anything in the workflow, etc.
generic plugin now stops at first successful license identification