Refactor of single-timeseries and completion visualisations

Make the basic single timeseries/single tat graph the base view, which is extended from. Instead of extending from a particular implementation (i.e. completion rate)

Reduce the number of similar views achieving the same functionality by removing the availability specific graph views which only added particular options to standard views.
Move graph components into app/client
Remove files that are not used anywhere

I think these are left over from when we had toggles to show and hide the tables.
Merge pull request #758 from alphagov/refactor/completion-graphs

Refactor of single-timeseries and completion visualisations