Detail styling for account lists in reply dialog

* Use flex to lay out account lists
  * Stretch account entry to fill to end of row
  * Give account entry minimum width
  * Update margins and paddings accordingly

Change-Id: Id24f7cb67bb08816f9358098db8e538c4826052a

polygerrit-ui/app/elements/change/gr-reply-dialog/gr-reply-dialog.html

@@ -58,6 +58,7 @@ limitations under the License.
       }
       .peopleList {
         display: flex;
+        padding-top: .1em;
       }
       .peopleListLabel {
         color: #666;
@@ -65,7 +66,9 @@ limitations under the License.
         padding-right: .5em;
       }
       gr-account-list {
+        display: flex;
         flex: 1;
+        flex-wrap: wrap;
       }
       #reviewerConfirmationOverlay {
         padding: 1em;