Mesh Expressions

We used to have a category of expression that created new meshes. We never implemented one so we removed the designation from the gui. It would still be useful to implement them though.

This comes up every so often in requests for dealing with history data. For example, users want us to expose their various raw arrays and let them combine them (and slices of them, etc) into curves and meshes using expressions.

# Make point meshes
pointmesh(coord(mesh))
pointmesh(temp,pressure,velocity[0])

# Create a new mesh that I can warp. This seems useful since it makes
# a new mesh over which VisIt can iterate, using coordinates of my
# choosing
rm = rectilinearmesh([0.,2.*pi,10], [0.,1.,20])
# Warp the mesh into the polar example from yesterday
C = coord(rm)
Offset = {C[1] * cos(C[0]), C[1] * sin(c[0])}
Cm = Displace(rm, Offset - C)
# Map some other field onto the new displaced Cm mesh
Cm_field = conn_cmfe(<mesh:field>, Cm)