Improved & unified deprecation handling

* De-duplication now happens in core, not in reporters. This ensures that
  the console doesn't get flooded.
* Stack traces are opt-out, not opt-in.
* The current runnable is not reported or logged for certain deprecations
  where it's irrelevant.
* HtmlReporter shows stack traces in expandable widgets.
* Env#deprecated and Env#deprecatedOnceWithStack are merged.

src/html/_HTMLReporter.scss

@@ -231,6 +231,8 @@ body {
     }
 
     &.jasmine-warning {
+      margin-top: $margin-unit;
+      margin-bottom: $margin-unit;
       background-color: $pending-color;
       color: $text-color;
     }
@@ -386,4 +388,27 @@ body {
     background: white;
     white-space: pre;
   }
+
+  .jasmine-expander {
+    a {
+      display: block;
+      margin-left: $margin-unit;
+      color: blue;
+      text-decoration: underline;
+    }
+  }
+
+  .jasmine-expander-contents {
+    display: none;
+  }
+
+  .jasmine-expanded {
+    padding-bottom: 10px;
+  }
+
+  .jasmine-expanded .jasmine-expander-contents {
+    display: block;
+    margin-left: $margin-unit;
+    padding: 5px;
+  }
 }