Reduce cropping options

[adeane-ga]

Simple Change to clarify usage
Currently PyRate has 4 options to crop, would be better if we reduce to 2 because the others are redundant and confusing.

Current Options:
# ifgcropopt: 1 = minimum extent 2 = maximum extent 3 = crop 4 = no cropping

Proposed Change:
# ifgcropopt: 1 = crop 2 = no cropping

[mcgarth]

I agree with the proposed change, but I would suggest a binary-style switch:

# ifgcropopt: 0 = do not crop; 1 = crop

[adeane-ga]

I agree with the proposed change, but I would suggest a binary-style switch:

# ifgcropopt: 0 = do not crop; 1 = crop

Yeah I agree, makes sense.