Added a degree-7, 12 point quadrature rule for TRIs with positive weights.
Added a degree-7, 12 point quadrature rule for TRIs with
positive weights.

This rule is provably minimal in the number of points, and
it deprecates the degree-7, 13 point rule with negative
weight, *and* degree-6, 12 point rule previously in Libmesh.



git-svn-id: ffc1bc5b3feaf8644044862cc38c386ade156493@2934 434f946d-2f3d-0410-ba4c-cb9f52fb0dbf

certik/libmesh,certik/libmesh,certik/libmesh,certik/libmesh,certik/libmesh,certik/libmesh,certik/libmesh