[GEOS-5623] GSIP 92 - Allow plugins to modify WMS MapContent before map rendering
Merge pull request #132 from aaime/getmapcallback

[GEOS-5623] GSIP 92
Merge branch 'master' of git://github.com/geoserver/geoserver
Merge branch 'master' of github-opengeo:opengeo/geoserver