Make right panel a dark-panel instead of every descendant.

Also move bg color central.

res/css/structures/_FilePanel.scss

@@ -17,7 +17,6 @@ limitations under the License.
 .mx_FilePanel {
     order: 2;
     flex: 1 1 0;
-    background-color: $secondary-accent-color;
     overflow-y: auto;
 }
 

res/css/structures/_LeftPanel.scss

@@ -46,7 +46,6 @@ limitations under the License.
 }
 
 .mx_LeftPanel {
-    background-color: $secondary-accent-color;
     flex: 1;
     overflow-x: hidden;
     display: flex;

res/css/structures/_NotificationPanel.scss

@@ -17,7 +17,6 @@ limitations under the License.
 .mx_NotificationPanel {
     order: 2;
     flex: 1 1 0;
-    background-color: $secondary-accent-color;
     overflow-y: auto;
 }
 

res/css/structures/_RoomSubList.scss

@@ -45,7 +45,6 @@ limitations under the License.
     padding-top: 6px;
     padding-bottom: 6px;
     cursor: pointer;
-    background-color: $secondary-accent-color;
 }
 
 .mx_RoomSubList_label.mx_RoomSubList_fixed {

res/css/views/rooms/_MemberInfo.scss

@@ -15,7 +15,6 @@ limitations under the License.
 */
 
 .mx_MemberInfo {
-    background-color: $secondary-accent-color;
     display: flex;
     flex-direction: column;
     flex: 1;

res/css/views/rooms/_MemberList.scss

@@ -17,7 +17,6 @@ limitations under the License.
 .mx_MemberList,
 .mx_GroupMemberList,
 .mx_GroupRoomList {
-    background-color: $secondary-accent-color;
     flex: 1;
     display: flex;
     flex-direction: column;

res/css/views/rooms/_RoomList.scss

@@ -37,7 +37,6 @@ limitations under the License.
 }
 
 .mx_RoomList_emptySubListTip_container {
-    background-color: $secondary-accent-color;
     padding-left: 18px;
     padding-right: 18px;
     padding-top: 8px;

res/css/views/rooms/_RoomTile.scss

@@ -23,7 +23,6 @@ limitations under the License.
     margin: 0;
     padding: 2px 12px;
     position: relative;
-    background-color: $secondary-accent-color;
 }
 
 .mx_RoomTile_tooltip {

res/themes/dharma/css/_dharma.scss

@@ -180,7 +180,7 @@ $lightbox-border-color: #ffffff;
 // unused?
 $progressbar-color: #000;
 
-// form elements
+/*** form elements ***/
 
 // .mx_textinput is a container for a text input
 // + some other controls like buttons, ...
@@ -220,6 +220,11 @@ input[type=search] {
     min-width: 0;
 }
 
+/*** panels ***/
+.dark-panel {
+    background-color: $secondary-accent-color;
+}
+
 .dark-panel {
     :not(.mx_textinput) > input[type=text],
     :not(.mx_textinput) > input[type=search],