Only show first overload in a series of consecutive overload signatures for navigateTo
Finished up "overload collapsing" for navigate-to.

Current semantics:
  - If an overload lacks an implementation, go to the first implementation.
  - If an overload has any implementation, go to the first one.
  - If there are any declarations between an implementation and any overload, this will split the series of overloads (note that this is invalid code).
Merge pull request #804 from Microsoft/overwhelmedByOverloads

Only show first overload in a series of consecutive overload signatures