#92 remove unwanted matadata in nansat.export2thredds
#92: Change time dimension from int to float in nansat.export2thredds().
#92 add grid_mapping metadata to all bands in nansat.export2thredds().
#92 Get rid of some arguments of nansat.export2thredds().
#92 Fix a bug of nansat.export2thredds().
#92 dont limit export2thredds to longlat and stere projections
Merge branch 'issue92' into develop