WIP: Add SCIFIOService

NB: Contains snapshot dependency. Remove before merging with master

Adds a SCIFIOService interface, which all io.scif.* services now
extend. This allows for convenient Context creation by just specifying:
new Context(SCIFIOService.class), for example, without creating an
explicit list of services.

Removed TypedService, as it's now obsolete and SCIFIOService seems
better named.
AbstractImgIOComponent: update service list

Instead of using an explicit Service list when creating a new Context,
use SCIFIOService.class and ScijavaService.class.

This is a much more flexible notation that alleviates the need for
maintenance of this list.