Add Shallow Water module

[ejtovar]

This pull requests adds an updated module for the Shallow Water Equations.

• ShallowWater: remove old code
• ShallowWater: add HyperbolicSystem declaration; add skeleton
• ShallowWater: implement most HyperbolicSystem methods
• ShallowWater: add Makefile
• ShallowWater: fix apply_boundary_conditions function
• ShallowWater: reintroduce source terms
• ShallowWater: add initial state library
• ShallowWater: add approximate Riemann solver
• ShallowWater: implement indicator
• ShallowWater: implement limiter
• EquationDispatch: hook up ShallowWater module
• ShallowWater: add runtime parameters
• HyperbolicModule: remove stencil source infrastructure
• ShallowWater: update low and high order fluxes
• HyperbolicModule: bite the bullet and special case shallow water
• ShallowWater: update limiter to latest version
• Limiter: minor cosmetic changes, unify naming
• Indicator: add "indicator evc factor" runtime parameter
• HyperbolicSystem: unify relaxation parameter naming
• Tests: euler_aeos/verification-leblanc*: update for new relaxation constants
• ShallowWater: convert magic number to a runtime parameter
• ShallowWater: add nodal source functions to the HyperbolicSystem
• HyperbolicModule: add low and high order sources
• unify shallow water initial state library with other pdes. cleaning up initial states as well
• ShallowWater: precompute h_star
• ShallowWater: avoid unnecessary computations
• ShallowWater: small performance tweaks
• ShallowWater: Limiter: put back v2 limiter
• ShallowWater: make both limiters available
• ShallowWater: modify paraboloid initial state to have a different 1D state
• ShallowWater: avoid eps in entropy viscosity commutator
• ShallowWater: fix compilation when compiling for float
• COPYING: add LANL copyright statement
• ShallowWater: add unit and verification tests
• ShallowWater: add a comment, and guard an unusual configuration case