Resolve accessibility isssues

- Remove unecessary aria-roles
- Associate label elements with form elements
- Remove extraneous markup on Network settings page
- Update generic markup to use definition list when appropriate
- Add aria-labels and aria-expanded to accordion triggers

Tested: Accessibility issues tested in using Lighthouse in Chrome
Developer tools Audit section and Dequeue Axe extension. Manually tested clicking on labels
set focus on the form elements. Visually tested of the Network
Settings page in Chrome, Firefox, and Safari to verify layout changes.

Resolves openbmc/phosphor-webui#76

Signed-off-by: Derick Montague <derick.montague@ibm.com>
Change-Id: Ib974c623e9d3b74e74e1f374c21e8191732ec26a
diff --git a/app/configuration/styles/network.scss b/app/configuration/styles/network.scss
index 0a822bd..b0de4f7 100644
--- a/app/configuration/styles/network.scss
+++ b/app/configuration/styles/network.scss
@@ -14,12 +14,19 @@
     height: 2.1em;
     margin-bottom: 1.2em;
   }
-  label {
-    min-width: 300px;
+
+  .net-config__fieldset {
+    margin-bottom: 1.2rem;
+
+    legend {
+      padding-bottom: 0.5rem;
+    }
+
+    .net-config__fieldset-content {
+      padding-left: 1.8em;
+    }
   }
-  fieldset {
-    padding-left: 1.8em;
-  }
+
   .net-config__static-ip-wrap {
     width: 100%;
     padding-left: 0;
@@ -39,6 +46,13 @@
     margin-top: 3em;
     padding-top: 1em;
     border-top: 1px solid $medgrey;
+
+    &::after {
+      content: " ";
+      display: block;
+      clear: both;
+    }
+
     button {
       float: right;
       margin: .5em;