Considering a threshold for considering an effective landcover fraction

[kasra-keshavarz]

Suggested by @MIsmlAhmed

It would be interesting to consider a threshold for fractions of each GRU to be finally considered in the final drainage database of MESH setups.

The community is welcome to comment and suggest.

[kasra-keshavarz]

Also, GRUs with 0 values could be omitted by default by the package.

[kasra-keshavarz]

The workflows are available on SUMMAFlow, this will be integrated in this work as well.