angular/forms/selecting_multiple_checkboxes wrong generic types

Variable and function declared to be List<String> when they were
List<Map>. The errors were not reported because the list constant was
not typed; now it is.
Added MirrorsUsed to examples
More MirrorsUSed
Yet more @MirrorsUsed
Merge pull request #10 from chalin/patch-3-fix-erroneous-generic-types

angular/forms/selecting_multiple_checkboxes wrong generic types