Removes functionality to
* select PNG rendering mode
* automated fallback to PNG images for SVG rendering
* PNG mode related class and tests
However, PNG images received from mathoid / restbase are still stored.
Bug: T311620
Change-Id: I595926027433182cc0396570bc3f1ce0cd2cafb3
This is doing a bulk of the job of creating a service
for working with math modes configuration. There's
still things to do, like moving math mode names,
and perhaps depending on default user options to
provide a bit more convenience, but that will be the
next step.
Change-Id: I1259a93651920f44104f2f5135e3e620c858be8d
