cache-control headers in integrated wms, GEOS-5686

- cleanup interceptor, add max-age header from layer metadata if
  declared
- add test

Conflicts:

	src/gwc/src/test/java/org/geoserver/gwc/GWCIntegrationTest.java
GEOS-5704, GEOS-5703: fixing a couple of TurboJPEG issues
Simple update of the GDAL documentation, by updating the Imageio-ext version to 1.1.7
Merge pull request #192 from dromagnoli/2.3.x

 GEOS-5704, GEOS-5703: fixing a couple of TurboJPEG issues
Merge pull request #178 from ischneider/GEOS-5686-2.3.x

cache-control headers in integrated wms, GEOS-5686
GEOS5273: disabled entities evaluation for remote SLD files
GEOS5273: moved external entity setting to global configuration
GEOS5707: disabled entities evaluation in WFS POST requests
GEOS5273 - GEOS5707: created EntityResolverProvider
GEOS5273 - GEOS5707: relaxed NoExternalEntityResolver path checks for schema files
Merge pull request #193 from svzdvd/2.3.x-GEOS5273-sld-entities

GEOS-5273 and GEOS-5707 for 2.3.x
GEOS-5716 Reduce repeated setup need in securty tests

Conflicts:
	src/main/src/test/java/org/geoserver/security/auth/AuthenticationCacheFilterTest.java
GEOS-5710 GetLegendGraphic fails with a layergroup containing a coverage invisble at current scale
Cumulative Fix for GEOS-5698 and GEOS-5215, security GUI bugs
Adding a passwd element in the curl tutorial (Adding a PostGIS database)
fixing typo in python buffer example
GEOS-5725, catching exceptions resulting from request object handler
merged encoding from master
updated German properties files
GEOS-5641 : modified encoding for French properties file (thx to Oscar Fonts)