added biarc and Euler spiral parametric curves to brl/bbas/bvgl

This comes from Brown University's internal repository at LEMS,
at lemsvxl/basic/dbgl. This is part of an effort to contribute a new edge
detection code (a new symbolic edge linker) to the official VXL.

Author of Changes: Caio SOUZA <caioc2bolado@gmail.com>
Supervisor: Ricardo Fabbri <rfabbri@lems.brown.edu>
reverted spurious changes to sdet on commit a1e264