Add # of components getter to MultiShapeletBasis
Add method to compute convolution orders in advance.
Add vectorized evaluation to [Multi]ShapeletFunction

This is still not the most efficient method of shapelet
evaluation (that's MatrixBuilder), but it's faster and more
convenient than looping over pixels in Python.
Make it possible to pass ellipses to testing utility functions
Add MatrixBuilder, a unified interface for shapelet matrix evaluation

MatrixBuilder provides the functionality previously present in
MultiShapeletMatrixBuilder, ModelBuilder, and some private code
in meas_multifit's psf.cc, with a unified interface, better code
reuse, and a design more amenable to future micro-optimization.
Remove old MultiShapeletMatrixBuilder

This has been replaced by MatrixBuilder
Remove old ModelBuilder

Replaced by MatrixBuilder
Rename MultiShapeletFunction's "elements" to "components"

This brings MultiShapeletFunction's nomenclature in line with that used by
MultiShapeletBasis and MatrixBuilder.