Implement TypeContext
Move TypeSelection constructors to .cpp
Add method holder class's info to MethodInfo
Fixed a bug that method arguments' defSites were not defined
Fixed a bug that the analysis result of CALL got a TypeSelection of TypeSelection
Add TypeClassOrSubclass skelton (work in progress)
Implement TypeClassOrSubclass
Fixed a MethodInfo initialization bug
TypeLookup now doesn't hold method owner class info