Face Edge Loop Partitioning

### Purpose 

The core issue in #1934 is Revit's `Face` representation allows multiple outer `Edge` loops, which are not supported in a ProtoGeometry `Surface`.  Hence, extracting `Solid`s from a Revit `Element` would at times fail as a prerequisite for creating a `Solid` is correctly converting the `Face`s.

### Terminology (for reference)

In standard BRep (Boundary Representation) terminology:  

* A *Solid* is a closed topology of faces and edges.
* A *Face* is represented by an underlying analytical surface (usually parameterized in 2D) and a collection of edge loops that bound the surface.  A surface, of course, can have unlimited extent if not bound.
* An *Edge* is a curve, lying within a face, representing a boundary of a face.  Two adjacent faces in a solid share an edge.  A coedge constitutes a faces reference to an edge.
* An *Edge Loop* constitutes a multi-part trimming curve of an underlying analytical surface, made up of a close loop of coedges.  These allow us to "trim" a surface into a face.  Note that it's possible for edge loops to be nested within each other, allowing one to cut out inner regions of an outer edge loop.  

An unfortunate reality of things is that a ProtoGeometry `Surface` is actually, under the hood, an ASM face!  So, bear with me if the terminology seems mixed. This is odd, but it makes sense for users, who would prefer to not think about any of this kind of terminology.  

### Discussion

In Revit, unlike ProtoGeometry, Dynamo's core geometry library, it's possible for a single Revit `Face` to possess two disconnected edge loops that are *not* contained within each other.  This results in two *disconnected* components to a Revit `Face`, even though there is only one single underlying surface.  This is common throughout the solids used to represent Revit Walls.

This pull request adds support to partition the edge loops of a Revit `Face` into disconnected components, each representing a valid set of trimming loops for an ASM face.  This is done by a containment check of the edge loops done in the parameter space of the Surface.  Each edge loop is turned into a closed 2D polygon and containment of another face is checked by a standard algorithm.

Hence, there is now a 1-n mapping between a single Revit `Face` and ProtoGeometry `Surface`s when converted via ToProtoType(). Revit Reference's are still correctly assigned using the same tagging mechanism as before.


### Unit tests

This pull request adds additional tests using wall geometry taken from the "advanced" sample in Revit.  

### Screenshot

Here's all of the solid walls extracted from the advanced sample:

![wallelements](https://cloud.githubusercontent.com/assets/916345/3606796/cc1b47ca-0d3b-11e4-8cfd-64de00367b9d.PNG)


I renamed it to underscore to make that clear.  It's fine in this case and prevents a complicated for loop.