HDG Boundary Conditions

HDG boundary conditions implement boundary conditions for physics implemented in HDG Kernels. All hybridized boundary conditions should inherit from HDGIntegratedBC as at the present time all hybridized boundary conditions are imposed weakly. Classes derived from HDGIntegratedBC must implement the onBoundary virtual method. Like their HDGKernel counterparts, hybridized boundary conditions should populate the data members _PrimalMat, _LMMat, _PrimalLM, _LMPrimal, _PrimalVec, and _LMVec.