CASE statement

[Peter Baumann]

rasql should have a CASE statement similar to SQL:
CASE a
WHEN x0 THEN y0
WHEN x1 THEN y1
…
END

Use casses:

• This is expected to be much faster than the current way to do classification (such as terrain/bathymetry rendering).
• It is necessary to avoid division by zero in the NDVI=(a-b)/(a+b).