Need ANGLE in grid

[duvivier]

In order to correctly plot sea ice motion vectors in python the u and v velocities need to be rotated. In order to do this, a user needs the 'ANGLE' variable from the pop grid. I am currently reading this in directly from the pop gx1v7 grid file on Cheyenne, but it would be nice to have in the 'grid' variable from pop_tools as well.

[andersy005]

I am currently reading this in directly from the pop gx1v7 grid file on Cheyenne, but it would be nice to have in the 'grid' variable from pop_tools as well.

A pull request is welcome :) No pressure though. We're selectively constructing the returned grid dataset in this function:

pop-tools/pop_tools/grid.py

Line 107 in 6562432

def get_grid(grid_name, scrip=False):

, and I believe adding ANGLE to this dataset is a straightforward process for someone familiar with the grid/topography files