Ditch interfaces where possible

[LordZoltan]

• IResolveContext to be ditched in favour of non-virtual ResolveContext
• IContainer to be thrown away - Container will be the primary container API
• IContainerScope also removed in favour of ContainerScope
• IScopeFactory removed (not required)
• ICompiledTarget removed. Compilers now always produce factory delegates.

In doing this, also, move as many of the Resolve operations as possible to being first-class members on these types instead of relying on extension methods.

The primary motivation for this is performance (although note that poor performance is only really noticed in micro-benchmarks) - method calls via interface are significantly slower than direct calls and even to virtual methods of a class.