Add 2D PGA (Cl(2,0,1))

[kliment]

Adds a 2D version of the projective GA using Cl(2,0,1) - this is wonderful for working with lines, points, areas, angles and distances in the plane.

[lgtm-com]

This pull request introduces 1 alert when merging 7b163ae into a1b1ba3 - view on LGTM.com

new alerts:

• 1 for Modification of dictionary returned by locals()

[eric-wieser]

Could you add an entry to https://github.com/pygae/clifford/blob/master/docs/predefined-algebras.rst too?

[kliment]

Done

[lgtm-com]

This pull request introduces 1 alert when merging e526291 into a1b1ba3 - view on LGTM.com

new alerts:

• 1 for Modification of dictionary returned by locals()

[kliment]

Just checking, do you need anything more from my end to merge this?

[arsenovic]

@eric-wieser what do you think? not sure about the tests, but seems like a pretty simple addition?

[eric-wieser]

There was a discussion on our slack about what to name the algebra, we should check if that came to a conclusion before merging.