Initial implementation of CylindricalAirgap class which automates creation of multiple annuli between two radii

Problems with discontinuous material boundaries have fields which suffer from jump discontinuities
This means the divergence of the Maxwell stress tensor is impulsive at material interfaces
Evaluating net force/torque using body forces requires both volumetric and surface integrals in these cases
This is a nontrivial excercise

In the meantime, the next step will be to add a special calculation method for cylindrical airgaps

Implements SpatialForcing which allows, e.g., spatially varying current densities defined by lambda functions (e.g. sinusoids)
Implements tests for SpatialForcing using sinusoidal functions in test_Square and test_Circle
Begins implementation of tests on two circular annuli (test_Annuli)

Mesh::mesh_data() now returns a MeshData object containing a vector of Triangles instead of nested vectors
Added SquareOrder2 tests of second order triangular elements

Reorganize some code into separate shared libraries

Store FiniteElementMesh DiscreteRegions in std::map with Contour as key

Changes the way number of elements and unknowns are calculated in Physics
    This still needs some work
Adds FunctionArgument class for passing arguments to Forcing objects with multiple parameters
Adds test demonstrating parallelism using OpenMP

FiniteElementMesh remains templated to facilitate storage of variable order elements

This eliminates all Boost library dependencies

    Part of this involves using more shared pointers and vectors (as opposed to arrays) as certain member variables
    Some of that has been done, some work may (probably) still needs to be done
    It's been a few months since this has been looked at so it will require some review

This is a bit of a mess right now

Work on rotational motion and related boundary refinement
Output for vector plots
Starts on nonlinear material properties
Begin encapsulating solver routines

Mesh::smooth() is based on satisfaction of a Laplacian condition

MappedBoundaryPair guarantees correct behavior of PeriodicBoundaryConditions when the UniformDiscretization option is set to false

Implement more rotational motion tests

Implement more rotational motion tests

Changes a DiscreteBoundary<2> to a DiscontinuousBoundary<2> This will be used for implementing relative motion in a user friendly way

This is a new route for implementation of relative motion. Renames Boundary to DiscreteBoundary (to differentiate from Sketch::ContinuousBoundary)

Fix minor inconsistency with antiperiodic boundary conditions

Begin implementation of PeriodicBoundaryCondition construction from PeriodicBoundaryPairs

Still need to work on special boundary types (e.g. sliding interfacing and periodic boundaries)

Expanded on magnetostatic testing with a uniform current density on a circular domain

Nodes, Triangles, Regions are complete (except material properties). Still need to work on Boundaries.

Paves the way for local region refinement. Necessary for converting refineable mesh to FEA discretization.

This is groundwork for the initial implementation strategy for virtual motion with node renumbering and periodic boundary constraints in the FEA solvers

Modification was necessary to introduce uniform boundary discretizations.

More work may be needed to make this fully robust.

Some infrastructure changes for implementing boundaries with uniform discretizations

Allows for two-way traversal between Edges and DartConstraint