Temporal activities no longer have a generalised extension method
for registering them with a service collecton. It is still static and has
the same rough shape as an extension method. This way it is less
visible and less likely to be called by accident.
Also in-line with changes in this branch, things have been renamed
Timers → Temporal
The project/NuGet package for implementation logic relating to
temporal actions has been renamed:
Elsa.Activities.Timers.Hangfire → Elsa.Activities.Temporal.Hangfire
Elsa.Activities.Timers.Quartz → Elsa.Activities.Temporal.Quartz
Whilst large numbers of C# files are "changed" by this commit,
it's just a straight move to a new path.
