Get rid of type piracy on DataInterpolations for SparseConnectivityTracer

[SouthEndMusic]

#1606 introduces type piracy on DataInterpolations to create a custom overload of interpolation evaluation for SparseConnectivityTracer, see also the Aqua test. This can be removed when SparseConnectivityTracer introduces their own support for DataInterpolations, which they will probably do as indicated here.

[adrhill]

We've got some shiny new doc-pages in SCT, including one on how to add overloads.

Feel free to open a PR with a SparseConnectivityTracerDataInterpolationsExt, even if it just implements the minimal set of functions you need. Let me know if things are unclear or if you need some help!

[SouthEndMusic]

@adrhill thanks for the heads up!