Support class methods and class / class instance variables

[redneckbeard]

Two key components to parsing and type inference on class methods: method storage/resolution and variable storage/resolution. This should be relatively straightforward if duplicative of the existing plumbing for instance methods/variables.

Compilation to handle class methods and class instance variables should probably target a separate struct type ClassFoo and is then embedded in struct type Foo with a field name of Self for simplicity.

Actual class/static variables should probably be package-level variables with a qualifying name, e.g. @@bar inside class Foo can compile to ClassVarFooBar.