First release of serial shallow-water version

This is the first step to a new dynamical core. We have chosen the vector-invariant form of horizontal momentum equations, in which we discovered that the polar relative vorticity is the key to eliminate polar numerical noise showing in the lat-lon grid. We place U wind component on the Poles, and redefine the polar relative vorticity by using Stokes' theorem. The new shallow-water version is free from polar noise.

In this version, we also implemented a moving reduced tendencies scheme, which can improve the computational stability at the polar region. The time step size can be increased by 60 times or so.