Reference Cell Area for sectors: File Loading

- new AppState property resultsReferenceCellsAvailable
- FileLoader signals presence of reference cell data for each file via
new property in FileStatistics
- AppView updates AppState if any of the loaded files had reference cell
data
Define a constructor for the result-by-element filter
- new type "ResultsFilterQuery" instead of a plain {} object literal
Reference Cell Area for sectors: Sidebar controls
- new "filter by refcell" button for each sector item in InfoView
- the ResultsFilterQuery's topic is set according to the clicked button (primary or refcell)
- UI markup template and CSS changes
Reference Cell Area for sectors: Result marker filter update
- isResultMatchingSector() compares result attributes against query parameters according to the query topic
Indicate result filter topic in "title" for FilterView
Merge branch 'filter-ref-cell-area'