The phrase "this cone cannot be..." can be misinterpreted as making a
value judgment about the given cone, rather than a blanket statement
about the argument (self) to these two functions. This commit changes
it to "cone should not be..." to indicate that the user should not
pass in either a trivial cone or the ambient space.

…e().

The error message output when _random_admissible_cone() receives an
invalid ambient dimension was a full sentence. This commit pares it
down to just the important part; amely, that there are no nontrivial
cones in the ambient dimension.

The line "G_index_sets = list(gevp_licis(G))" appears twice in EXAMPLES,
but the variable "G_index_sets" is not used thereafter. It was most
likely copy/pasted into the example by mistake. This commit removes it.

…30605.

Thanks to some recent improvements in cone containment testing, we no
longer have to reimplement it for vectors with irrational entries
ourselves.

The sage library is now doctested with a random random seed (imagine),
making most calls to set_random_seed() superfluous. We remove a few
from the cone critical angle code here.

The solve_gevp_zero() and solve_gevp_nonzero() functions for cone
critical angles are "internal" and can return generators. Likewise for
the testing function _solve_gevp_naive(). This should be a tiny bit
more efficient.

…metic.

Passing exact=False to either the max_angle() or critical_angles()
method of cones is a bit "dangerous" because we can miss eigenspaces
of dimension >= 2 due to numerical issues. Add a warning to the
docstring about it.

…s.py.

Two tests in this module imported the gevp_licis() function but then
did not use it. No longer.

We already have a matroid method that does more or less what the new
gevp_licis() function does in cone_critical_angles.py. It's faster to
use the matroid implementation and then tweak its output slightly, so
let's do that instead.

For reasons I've long forgotten, the cone max/critical angles
algorithms were using QQbar for "rationals with roots." Switching it
to AA causes no problems now, and is clearly preferable (the only
eigenvalues we compute are of positive-definite matrices).

…not"

…calls

…call

…atrices

…nonzero()

Using the identity M[I,J].transpose() == M.transpose()[J,I], we can
avoid transposing M itself and instead transpose the smaller M[I,J]
when M[I,J] is already known.

…ning

The existing warning about this module being internal is easy to
miss. This one should appear in bright red at the top of the module
documentation.

…ngles

This is an internal module, but it's fully documented and nice to have
access to the implementation behind the max_angle() function. Despite
being documented, the functions in cone_critical_angles.py are subject
to change at any time. This itself is loudly documented.