Add Ability to Measure Properties of Geometry/Topology

[jmwright]

This requires selection of vertices, edges and faces to be working first.

Possible Workflows

• Select edge directly to get curve length, and maybe start and end vertex vectors.
• Select two vertices to get the curve length between them, and maybe the start and end vertex vectors.
• Select a vertex to get its location vector.
• Select a face to get its area, and possible edge and vertex info as well.
• Multi-selection of faces could maybe give a combined area.
• Select a component to give volume, and maybe face, edge and vertex info.