Improve security for the proxy view.  Fixes #1308.

* In production, the proxy will only respond to hosts  listed in the settings.PROXY_ALLOWED_HOSTS tuple and the OGC_SERVER hostname.

* Remove the pass through authentication headers.  Pass through authentication headers were getting added to requests outside of their respective realm.

* Add a PROXY_URL setting so administrators can use proxies other than the GeoNode.

* Only forward session cookies to the OWS url since commit ef1cf1 states that session cookies can influence local OWS GetCapabilities requests.
Merge pull request #1315 from garnertb/proxy

Improve security for the proxy view.  Fixes #1308.
Updated changelog for version 2.0c7
add missing double quotes in layer detail
add missing slash in proxy url
fix the clear options button in advanced search
keep open the type filters
This fixes #1311, thanks @bartvde!
Merge pull request #1316 from capooti/issue-1311

This fixes #1311, thanks @bartvde!
Fix typo in the default PROXY_URL setting.
Updated changelog for version 2.0c8
Update dns entry on jenkins-geonode-aws.sh
Merge branch 'master' of github.com:GeoNode/geonode
Use existing venv for aws task
Remove trailing slash in jenknis-geonode-aws.sh
Merge branch 'master' of https://github.com/GeoNode/geonode