[fix bug 968094] Wrong text at ng-reports section of the dashboard

This change is the fix for bug https://bugzilla.mozilla.org/show_bug.cgi?id=968094 (968094-Wrong text at ng-reports section of the dashboard).

Issue caused: In dashboard, the text for some quantitative values in ng_reports section were wrong. For example, the singular quantitative value like '1 activity' or '1 day' was appearing in plural form as '1 activities' and '1 days'.

Resolution: count_ng_reports is the method which filters the ng_reports on arguments and returns the count of results. Check for count; if (count equals 1) use singular word; if (count greater than 1)use plural word; if (count equal 0 or less than 0) use 0.