Add something in the OSCAR manual on solving systems of polynomial equations

[fingolfin]

I.e. how to do it at all, and some hints for options to tune things / selecting different algorithms etc.

@micjoswig is very much interested in this. Of course @ederc is a leading expert on this and hopefully can contribute a rough draft as a starting point. @micjoswig knows a phd student who is interested in this and could contribute to polishing this.

Aiming a little higher we could also provide a tutorial for this, once we have the basics.

There is also a chapter in the OSCAR book which may be helpful for this.

[micjoswig]

Thanks, @ederc for taking the lead here.

Please notify @ooinaruhugh @fpnowell about any draft that you might come up with.