Management of NO_DATA in BandMath

Short summary of the requested feature

When appliyin the BandMath application, the result of an operation with a NO_DATA pixel should return another NO_DATA.

Exemple : im1.tif = input image with all pixels as "No_DATA" (NoData Value=-32768)

otbcli_BandMath -il im1.tif -out output.tif -exp 'im1b1+5'

Output.tif has the value 5 everywhere