Removed deprecated custom season categorisation functions.
Removed deprecated shortname categorisation functions.
Changed default names in some categorisation functions.

The deprecation period for default name changes has ended and the
new names are now defaults and warnings are removed.
Removed tests for categorisation function deprecations.
Updated copyright notice.
Merge pull request #903 from ajdawson/season-deprecations

Remove deprecations from coord_categorisation module
Merge branch 'master' of https://github.com/SciTools/iris into coord_dims_with_str
fixed copyright dates