create GenericPixelFunctionPixel
create_VRT_from_ADS() in envisat.py: choose create one-line band or full-size band by "caliblation" argument.
mapper_asar.py: add "caliblation" parameter. user can choose how to create sigma0, ice and water bands, from one-line Inc.Ang band or full-size Inc.Ang band.
It is not ensured that projection is available form the first subdataset.
Therefore, if projection form a subdataset is empty, try to get from the next subdataset.
#98 comment6 : Remove pixelfunctions form one-line and one-pixel bands.
Add set_defaults() function to use #108.
#108 : get kwargs from Nansat to mapper.__init__() and pass it to VRT
#108 > nansat.py : get kwargs in __init__() and pass it to mapper.__init__().
vrt.py : get kwargs from each mapper.
#113 and #116 
If file name starts from "ASA_" and eResampleAlg is default(average) in resize(),
change eResampleAlg to 'NearestNeighbour'.
BetaSigmaToIncidence() in pixelfunctions returns GDT_Float64 even if input data are complex number.
So data type of the 5th band is always Float64(6).
choose if add geolocration for ASAR and MERIS by kwargs. (#117)
change kwargs in mappers.
LANDSAT8 has different size bands.
If band sizes are different from the 1st band, they are unified by changing DstRect in VRT.
trying to merge with remote