Bug fix: Pressing <Enter> key instead [Search] button sends only Simple Search request.

Fix for the bug: Pressing <Enter> key instead [Search] button sends only Simple Search request: Bug: http://trac.osgeo.org/geonetwork/ticket/1041
Discussion: 
http://osgeo-org.1560.x6.nabble.com/GeoNetwork-opensource-Developer-website-1041-Pressing-lt-Enter-gt-key-instead-Search-button-sends-on-td5000720.html