WIP(document): selenium tests are more clearly structured
WIP(document): selenium tests are more clearly structured

Selenium is initialized and closed at the module level.

Code manipulating django and selenium is now a separate class.

CaretInParagraphTests is broken down into a base, with testing code,
and smaller subclasses, with parts of the case data.

fiduswriter/fiduswriter,fiduswriter/fiduswriter,fiduswriter/fiduswriter,fiduswriter/fiduswriter