Fix DDS/BIL plugin tests

This patch fixes failing tests in the DDS plugin. The failures are due to two issues:
1) The test file (aus_dem.tif) was not deployed to the build directory, leading to resource not found errors. Renaming the file with a .tiff extension resolves this problem. (The top level pom files defines *.tiff as a resource pattern, but not *.tif.)
2) The tests incorrectly interpreted binary content as character content, leading to unexpected content lengths.