More infrastructure work for periodic b.c.s

Simplification and clarification of (discrete) boundary conditions effecting the implementation of FiniteElementMesh classes

Framework for multi-material magnetic models and testing of linear material properties with relative permeability > 1

Infrastructure and planning for multi-material models

Elaboration of TwoRegionHex magnetostatic_forcing tests

Started implementation of Magnetostatic solver
Work on Dirichlet boundary conditions (magnetic insulation)

Work on HomogeneousForcing for Poisson-like equations
Started implementation of Magnetostatic solver

Work on HomogeneousForcing for Poisson-like equations
Started implementation of Physics template interface

Work on HomogeneousForcing for Poisson-like equations
Started implementation of Physics template interface

Refactor tests and matrix construction to utilize interfaces for XMatrixGroup classes

* Translate tests from CMake to GoogleTest
* Split Branch/Star/Constellation into multiple files
* Update Sketch.save_as to create directory if it does not exist using Boost::Filesystem
* Split Constraint.h/Constraint.cpp into multiple h/cpp files
* Split Pattern.h/Pattern.cpp into multiple h/cpp files
* Separate mesh/Point class in to own Point.h/Point.cpp files
* Separate mesh/utility functions into own util.h/util.cpp files
* Fixed problem with Sketch Contour/Boundary parsing related to supremum calculations
* Added .oesk extension for sketch output files
* Added .oeme extension for mesh output files
* Add build_gallery.py python script. Parses ./build/test/output directory for .oesk and .oeme files and saves images using matplotlib
* Removed using namespace std
* Updated implementation of RotateCopy
* Added RemoveInternalBoundary option to Pattern and subclasses
* Rewrote Mesh::locate_triangle function
* Changed type of Mesh.Points from vector<Point*> to vector<Point>
* Changed Edge members from type Edge* to type size_t
* Cleanup of Edge and Node access interface in Mesh
* Change Mesh::Edges from type std::vector<Edge*> to std::Vector<Edge>
* Add std::vector<DartConstraint> Constraints to Mesh. Revamp of constraint handling.
* Change Sketch Variable and Vertex vectors from raw pointers to shared pointers
* Change Sketch Boundary and Contour vector from raw pointers to shared pointers
* Change Sketch Pattern vector from raw pointers to shared pointers
* Change Sketch Constraint and Curve vectors from raw pointers to shared pointers
* Fix memory leaks
* Cleanup of Sketch and reorganization of dependencies
* Add shared_ptr const correctness to Sketch
* Robustified implementation of Sketch::solve()
* Started refactorization of mesh refinement control algorithm