Added an option to propagate parameter types to base methods

[lostmsu]

It is similar #194, in that the same types parameter types might be OK for base methods. It could happen when we just don't have any examples in the current code, that would give that kind of information to analyzer.

By default set to false to keep conservative behavior.

class Base:
  def foo(x):
    ...

class Derived(Base):
  def foo(x):
    ...

Derived().foo(42)

# Base().foo(42) is actually also called, but not in this project

[MikhailArkhipov]

Is there case when we don't want this?

[lostmsu]

In A: B, B: C case, when we see b:B = ..., b.foo(SomeType()), b can be either of A and B. So, assuming substitution principle, B.foo should propagate to A.foo. However, there's no principle, that would tell, that C.foo should also take an instance of SomeType. At best, its an lucky guess.

So I think its good to have an option.

Now for my purposes, I need it true. But you guys can decide for the default value.

[MikhailArkhipov]

I mean, it is not something that user sets so it it typically set by the application one way or another. #261 may be related.