Steering has removed the thumbnails property from image fields and we
can now request arbitrary images sizes from the image render API.

Up until now the calendar kept a single record of calendar events. This
record was modified whenever new or other events needed to be displayed.
Events were added/changed/removed imperatively (i.e. when
entering/leaving conflict mode), which goes against the principle of
unidirectional data flow embraced by Vue and other reactive frameworks.

The calendar is now split into separate components most importantly the
normal week view and a separate conflict view with separate state
management. The state management itself has been reworked and improved
so that it uses unidirectional data flow.

These changes massively improve performance, simplify state management,
and should make it easier to reason about the code (conflict mode was
hard!).

fixes #287

refs #186

refs #179

API object attribute names are now:

1. camelCased (#164)
2. use Id / Ids suffix for object references (#172)