Fix 'specifc' typo in glossary
Fix partial sentence so it makes sense
Update Hits description in glossary

We now exclude images from the hits import, so they won't show up
in the app.
Use a less ambiguous example TNA timestamp

For 2 February, it's not immediately clear which '02' refers to the
month and which to the day.
Add 'Canonical' to the glossary

This comes from the glossary blog post:

    https://transition.blog.gov.uk/2014/03/17/transition-technical-glossary/
Merge pull request #222 from alphagov/glossary-fixes

Glossary fixes