Emulated Type Initializers

[Washi1337]

Includes the following changes:

• Adds RuntimeTypeManager which manages type initialization and can redirect control to a static class constructor (.cctor) if it is available.
• Ensures call and field opcodes are first redirected to type initializers when required.
• Ensures static fields are initialized with their initial value stored in FieldRva

This does not include special handling of beforefieldinit flagged types yet. This will have to be postponed until CIL method body verification is implemented.