- Fixes #496, an error when finding reference on namespaces defined in
metadata
- Groups all namespace definitions & references under a single node,
which itself is non-navigable. Prior to this change, there would be lots
of top-level nodes for the same namespace with 0 references.

Fixes internal issue #1138943.

In the SymbolFinder API, references to constructors are included as references to both the constructor method symbol and the related type symbol. Because reference locations are deduplicated across all results shown in Find References, we have to decide which definition node to use as the parent. Prior to this change the first related definition returned to us by the SymbolFinder won, but this ordering was not guaranteed to be consistent. This change introduces a precedence ordering for definitions returned by the SymbolFinder that currently guarantees that members will be preferred over types.

Additionally, this change removes the requirement that definitions shown in Find References have distinct locations. This allows us to meaningfully separate references between a type and its default constructor which has the same location.

This will be used by TypeScript so it can display FindRefernces result in a
tree form similar to how C#/VB does it.  i.e. it can show results like:

Decl1
|--Ref1
|--Ref2
Decl2
|--Ref3
|--Ref4

* Display logical path rather than full file path. I.e.
<ProjectName>\<Folders>\<FileName>
* Use gray text to indicate definitions that have no references rather
than definitions defined in metadata.
* Show "(0 references)" when there aren't any found.
* Don't fully-qualify definitions.

In this initial implementation, find references results are now grouped by the definition that they directly reference.

For symbols defined in metadata, we previously showed the references without showing the definition itself. We now show the metadata definition as well.