Add a startwith param on suggestion search service

http://trac.osgeo.org/geonetwork/ticket/1148

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 http://localhost:8080/geonetwork/srv/fre/main.search.suggest?field=any&startwith=true&q=cor

if startwith=true, then main.search.suggest will return only suggestions that startwith the q param

OpenSearchSuggestionTextField? UI class will now take the param startwith (by default false) to active or not this feature.