Added option -G to get listing of supported raster types instead of calling ST_GDALDr...

Added option -G to get listing of supported raster types instead of calling ST_GDALDrivers in SQL.  Had to tweak rt_raster_gdal_drivers in rt_api.c to not limit drivers based upon creation capabilities.  Associated ticket is #1374.
Added ability to specify band indices with ranges for option -b.  Example: -b 1-5,7,9-15.  Associated ticket is #1375.
Added warning messages when loader is processing more than one raster and rasters may have different number of bands, pixel types, hasnodata flags, NODATA values, geotransforms andtile sizes.  Associated ticket is #153.

git-svn-id: http://svn.osgeo.org/postgis/trunk@8418 b70326c6-7e19-0410-871a-916f4a2858ee