* Move derivative taker to a separate file

* Add fold markers

* fix docs

* Add SpatialConstant

* Add docs

* Improve docs around SpatialConstant, ExpressionKernel

Co-authored-by: Andreas Kloeckner <inform@tiker.net>

* Use a separate class for M2L translation

* Fix docs and caching

* M2L Translation Factory

* vim markers

* Fix tests

* Fix toys

* Fix test_m2l_toeplitz

* Fix more tests

* Use a better rscale to get the test passing

* Use pytential dev branch

* Try 2r/order instead of r/order

* Use downloaded shared sphinxconfig

* Make doc index incrementally more welcoming

https://github.com/inducer/modepy/pull/38#issuecomment-846472970

This reverts merge request !31

This reverts merge request !26