refactored sample.search to use ml-search-ng.

rewrote search ctrl and template
replaced search form in index.html with ml-remote-input directive
removed facets and results directives (superseded by ml-search-ng directives)
removed sample.common/MLRest (superseded by ml.common/MLRest)
renamed MLQueryBuilder -> MLSampleQueryBuilder (avoid name collision with ml.common/MLQueryBuilder)
removed dependency on mlFacets (unused, obsolete)