Allow full circles to be exactly represented and fix bug in CircleArc quantization which was sometimes converting small degenerate input arcs into very large arcs

* Some exact predicates have been changed so that an arc that starts and ends on the same vertex is treated as a full circle (Previously a repeated vertex was assumed to be a zero length arc)
* Unit test added to check splitting and unquantization of ExactCircleArc contours containing full circles with no interesections
* Add Vector::repeat(const T& constant)
Merge branch 'master' of github.com:otherlab/geode
Merge branch 'master' of github.com:otherlab/geode