Add counts to Dashboard (#2)

Also refactored database parameters with a few extension methods; ready for profile view page

src/JobsJobsJobs/Shared/Api/Count.cs

@@ -0,0 +1,7 @@
+namespace JobsJobsJobs.Shared.Api
+{
+    /// <summary>
+    /// A transport mechanism to send counts across the wire via JSON
+    /// </summary>
+    public record Count(long Value);
+}