Revert "Implemented reduced method model."

This reverts commit aaf2b919f59f4948d7b73870b3e8d872a0cd6ee0.
Revert "Implemented better way to handle extension method invocations."

This reverts commit d4afc75413fbc8c9b82a96c7b2e2459ceb583c1e.
Revert "[TypeSystem] Specialized method now contains a flag specifying the"

This reverts commit bd1811cc18eb6343a954e6dfda35577b6b1109fc.

Conflicts:
	ICSharpCode.NRefactory.CSharp/Resolver/OverloadResolution.cs