cache-control headers in integrated wms, GEOS-5686

- cleanup interceptor, add max-age header from layer metadata if
  declared
- add test
GEOS-5704, GEOS-5703: fixing a couple of TurboJPEG issues
Simple update of the GDAL documentation, by updating the Imageio-ext version from 1.1.6 to 1.1.7
Merge pull request #191 from dromagnoli/2.2.x

GEOS-5704, GEOS-5703: fixing a couple of TurboJPEG issues
Merge pull request #177 from ischneider/GEOS-5686-2.2.x

cache-control headers in integrated wms, GEOS-5686