Revert "deegree-tilestore-gdal: caching of datasets in thread local implemented"

This reverts commit d85a3b94682c7f3b97b0eb37ceda053bd838838e.
deegree-tilestore-gdal: support for rasters without transparency band
deegree-tilestore-gdal: proper image format support implemented
deegree-tilestore-gdal: jpeg transparency workaround
deegree-services-commons: NPE fix