add primitive polynomials up to degree 27

[pcaspers]

Opening this for discussion ... I added primitive polynomials up to degree 27 using the python package Galois. The addition of the source code seems to require around 25 MB of additional space in the repository, so I am not sure if we want to do this.

Apart from the repo size:

• I don't see any issue with compilation times even when including all polynomials
• the ql lib binary goes up from 40 to 100 MB on my mac when including all polynomials
• but the user can decide via PPMT_MAX_DIM which max dimension is required and only the necessary polynomial data will be included in the build, we can of course leave this value at 21200 (or maybe increase it a bit)

[pcaspers]

test times are failing for some unit tests because their "problem size" use the updated PPMT_MAX_DIM - I just leave it as is for the time being until we have decided what to do with the change

[coveralls]

coverage: 72.609%. remained the same
when pulling 1dab288 on pcaspers:add_primitive_polynomials_degree_27
into c812b75 on lballabio:master.

[lballabio]

Just throwing it out there—what if we gave the library a method to read additional polynomials from a file, instead of having them in the code? Thoughts?

[pcaspers]

Yes maybe. Where would we provide this file?

Another idea I had was to create a subrepo with a cpp-file containing the additional polynomials. Cloning the subrepo is optional and the file is included in primitivepolynomials.cpp if the higher degrees are required via PPMT_MAX_DEGREE.

[github-actions]

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[lballabio]

I'd avoid compile-time switches because, for instance, we can only provide one choice in the Python wheels on PyPI.
A method to load additional polynomials from a file (that we might not even provide ourselves—it could be available from ORE's site, for example) would leave the choice open.