added function to reset the Catalog paths

[ChrisBarker-NOAA]

Quick kludge to add a function to reset the CAT_PATH_* dirs.

You should be able to call set_cat_paths(a_new_path) after importing and away you go.

But I haven't actually tested that -- there may be some more reconfiguration that needs to be done,

But as it is -- nothing's different than it was if you don't call that function

[ChrisBarker-NOAA]

Side note -- It would be better if the:

Fresh parameters: how long until model output avialability will be refreshed

for find_availabililty() if requested

FRESH

stuff was part of the catalog yaml file, rather than here.

-CHB