Move IRasterIO implementation from RasterBand to Dataset in order to minimize the number of database queries
Correct memory management in IRasterIO
Corrections: IRasterIO in band calls RasterIO in Dataset.
Overview tables are used when needed
Last changes to ensure overview tables are properly read. Not sure if it works. Better test before using this.
Merge branch 'release/GDAL_110' into develop
Merge branch 'release/GDAL_110' into develop

Conflicts:
	postgisraster.h
	postgisrasterrasterband.cpp
Merge branch 'develop'. New improvements made on the driver go in develop too.