Merge pull request #8 from knutfrode/master

Small update of sar_wind.py to also work for ASAR images
Print gribfilename to ease (manual) copying from server to local dir and later offline use. Added a break in the for-loops to use the first directory found. Note that we plan a major change of model_wind.py to make it more generic (#1).
changed test for whether wind has already been calculated
merged develop into master, and changed sar_wind.py to not add look direction to SARWind object if it already exists
Updated help