Work with multiple spectral sequences

[dalcde]

For example, if we want to work with the ASS for S/p, there are maps S -> S/p -> S^1 and we want to be able to simultaneously work with these two spectral sequences and propagate differentials between. This will require some significant work in ext-websocket/sseq.rs to deal with multiple spectral sequences and maps between them, but essentially no work is required on the resolver side (perhaps apart from fixing SpectralSequences/ext#45)

If SpectralSequences/ext#27 is implemented, this should take that into account as well.

[hoodmane]

This will be done in my new front end:
https://github.com/SpectralSequences/webserver/