Rework custom status context menu

This updates the custom status context menu to match the latest comps.  A single
button is used for setting / clearing, depending on what is appropriate.

The state logic is also changed to depend on events and storage from js-sdk for
the committed status message.  This makes it easy to distinguish the value being
edited from what's currently committed.

res/themes/dharma/css/_dharma.scss

@@ -68,7 +68,7 @@ $event-selected-color: #f7f7f7;
 $primary-hairline-color: #e5e5e5;
 
 // used for the border of input text fields
-$input-border-color: #f0f0f0;
+$input-border-color: #e7e7e7;
 $input-darker-bg-color: rgba(193, 201, 214, 0.29);
 $input-darker-fg-color: #9fa9ba;
 $input-lighter-bg-color: #f2f5f8;
@@ -192,6 +192,8 @@ $progressbar-color: #000;
 
 $room-warning-bg-color: #fff8e3;
 
+$memberstatus-placeholder-color: $roomtile-name-color;
+
 /*** form elements ***/
 
 // .mx_textinput is a container for a text input

res/themes/light/css/_base.scss

@@ -188,6 +188,8 @@ $progressbar-color: #000;
 
 $room-warning-bg-color: #fff8e3;
 
+$memberstatus-placeholder-color: $roomtile-name-color;
+
 // ***** Mixins! *****
 
 @define-mixin mx_DialogButton {