Alter occurence within vicinity fill value. (#1226)
Alter occurence within vicinity fill value. (#1226)

Occurence within vicinity does not want to propagate values from 
underneath masked regions. However, the maximum_filter function taking 
from scitools does not handle nan values that have been used to fill the 
mask. Thus they can be propagated into unmasked regions. By using 
-np.inf as the fill value instead, the maximum_filter will not choose 
these values.
metoppv/improver,fionaRust/improver,fionaRust/improver,metoppv/improver