For text searches, add 'equals' and 'does not equal'.

[claremacrae]

All the text filters in Tasks offer includes and does not include. I had been wondering if anyone would want alternatives to that search mode, and the answer is yes: #741

This is to capture my suggested fix for #741 which is, for text searches, to add these extra search choices::

• equals
• does not equal

It's easy to see others being added later on.