Split IStartup registration and initialization into two seperate concerns

[thecodejunkie]

Today an IStartup lets you both register dependencies and perform initialization work. This makes ordering in the Bootstrapper initialization method tricky. We should split the concerns into two interfaces

• IApplicationStartup - Lets you do Initialize
• IApplicationRegistrations - Lets you do TypeRegistrations, CollectionTypeRegistrations and InstanceRegistrations

IApplicationRegistrations should happen before IStartup in the Bootstrapper.Initialise() method.

This will also bring the functionality up to par with the changes that was introduced with ConfigureApplicationContainer/ConfigureRequestContainer and ApplicationStartup/RequestStartup

NOTE We probably should also introduce IRequestStartup and IRequestRegistrations