* mimic numpy's norm when ord==None

- When ord==None, numpy ravels the array and then computes the euclidean
  norm.

* test norm when ord is None

* fixup! mimic numpy's norm when ord==None

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

* implement PyOpenCLArrayContext.ravel

* fixup! implement PyOpenCLArrayContext.ravel

- order="K" was only correct for >0 stride values, instead renamed it to
  order="A" as per numpy.

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

* Add a longer explainer on freeze and thaw

* Add ArrayContext.clone

* with_container_arithmetic: Add _same_cls_check

* Add test for error-on-mixed-array-contexts

* Improvements/fixes to freeze/thaw explainer

Co-authored-by: Alex Fikl <alexfikl@gmail.com>

* Remove trailing whitespace (flake8)

* Add link to lazy eval functionality under the hood of freeze/thaw

* Stop using code injection for actx match checking in with_container_arithmetic

* Make usage guidelines for freeze/thaw a separate section

Co-authored-by: Thomas H. Gibson <gibsonthomas1120@hotmail.com>

* Tweak phrasing in freeze/thaw usage guidelines, add anchors

* Remove an extraneous word in the freeze/thaw description

Co-authored-by: Alex Fikl <alexfikl@gmail.com>
Co-authored-by: Thomas H. Gibson <gibsonthomas1120@hotmail.com>

This reverts commit a1b97a66.

* Implement, test container-over-container broadcasting

* Tweak bcast_container_types arg doc

Co-authored-by: Alex Fikl <alexfikl@gmail.com>

* Improvements to with_container_arithmetic

- Support matmul with a separate operator class
- Join container and number broadcasting code paths
- Make args keyword-only

Co-authored-by: Alex Fikl <alexfikl@gmail.com>

* Move array context functionality over from meshmode

Co-authored-by: Alex Fikl <alexfikl@gmail.com>

* Drop sphinx version requirement

* Fix replica DOFArray in tests for pylint

Co-authored-by: Alex Fikl <alexfikl@gmail.com>