MemberNameEqualsClassName ignores functions which return a single expression

[schalkms]

As mentioned in #653
this rule ignores functions which return a single expression since detekt cannot infer the type (at the moment).
Consider the following code for example

open class A {
  companion object {
    // return type = A
    fun a(condition: Boolean) = if (condition) B() else C()
  }
}

class B: A()
class C: A()