Fixes NPE error when query string in tool.Search is null.
Adds @ToolUi.DropDown for displaying a simpler object selection if the user requests it.
Adds ToolPageContext.isObjectSelectDropDown and changes set/record field input processor to use it so that its display uses select[multiple] if @ToolUi.DropDown is specified.
Fixes page builder not working in multi-site environment.
Fixes filters heading sometimes not showing up in search.
Merge branch 'release/2.0'
Merge branch 'master' of github.com:perfectsense/brightspot-cms