[ctioga2] first tests for the clip/depth set of features

git-svn-id: svn+ssh://rubyforge.org/var/svn/ctioga2/trunk/ctioga2@533 86c91514-0d3b-42e0-aed1-4dfce116d947
[ctioga2] make xy-parametric style-aspect style accept - as delimiter too

git-svn-id: svn+ssh://rubyforge.org/var/svn/ctioga2/trunk/ctioga2@534 86c91514-0d3b-42e0-aed1-4dfce116d947
[ctioga2] refactor most of the duplicated code between the different plot-style-based elements, thereby making all plots types aware of the new depth and clipping capacities

git-svn-id: svn+ssh://rubyforge.org/var/svn/ctioga2/trunk/ctioga2@535 86c91514-0d3b-42e0-aed1-4dfce116d947