Expose additional std::vector API from Array.

Change-Id: I377322af0372a56500a9d2cc6b841e872e875f73
Expose more Eigen vector types in the Avogadro namespace.

Change-Id: Ia31edacf43865feaf9d0030321dc3c7758690110
Generalize rendering API, use Core::Array where possible.

* Rename Rendering::OverlayPass to Overlay2DPass
* Add an Overlay3DPass
* Allow separate specification of mesh vertices and triangle
  indices.
* Allow opacity to vary per mesh vertex.
* Generalize the BufferObject and ShaderProgram APIs to remove
  overloads and duplicated code.
* Allow TextProperty to use VectorXubs for colors.

Change-Id: I9d2195ca1900e9ac8cb5351fafa864150971a1ec
Add a LineStripGeometry drawable.

Change-Id: I9d6b44c9d87e440cb1ab853289c62a4b1ec802c1
Port the bondcentrictool from Avogadro 1.x.

Change-Id: I40cfaaf8f7f200aab2fd257063b883415e3bb1b5
Merge topic 'bondcentric' into master

190e41bb Port the bondcentrictool from Avogadro 1.x.
468cc787 Add a LineStripGeometry drawable.
a1e76f13 Generalize rendering API, use Core::Array where possible.
1be98bf2 Expose more Eigen vector types in the Avogadro namespace.
e19ebfbb Expose additional std::vector API from Array.