Wire up more properties in handlers and support flex.

A problem with extrapolation means that the interpolation tests in this CL don't test the property handler lists, as they are expected to fail.

I've bypassed the extrapolation bug locally in order to check this CL. The testing will work when the extrapolation bug is fixed.
We should stop using the pipe delimiters and just use an array of strings, the minifier could easily do this optimisation.