Enable screen sharing

For now, only the video is transmitted.
The camera is turned off when screensharing, just like on the desktop
app.

In CallProvider, replace `isVideoOn` state with `videoStatus` to toggle
between off, on or screenshare.
Add icon for when screenshare is active.
Remove screenshare button menu options, as they are unavailable on the
web.

Change-Id: I95dd1c18efd91ab8b9063f0e7f817839e4f24aba
diff --git a/client/src/components/SvgIcon.tsx b/client/src/components/SvgIcon.tsx
index 8f83587..1ef5f9d 100644
--- a/client/src/components/SvgIcon.tsx
+++ b/client/src/components/SvgIcon.tsx
@@ -721,6 +721,40 @@
   );
 };
 
+export const ScreenShareStopIcon = (props: SvgIconProps) => {
+  return (
+    <SvgIcon {...props} viewBox="0 0 24 24">
+      <path id="Path" d="M12.6,8.9V7.8l2.6,2.2l-2.6,2.2V11c-3.4,0.1-4.2,2.6-4.2,2.6C8.5,9.6,11.7,9,12.6,8.9z" />
+      <g id="Icons_Outline">
+        <g id="Laptop_Black_24dp">
+          <g transform="translate(2.000000, 5.000000)">
+            <g id="Shape">
+              <path
+                d="M17,12H2.8c-0.5,0-0.9-0.2-1.2-0.5C1.2,11.1,1,10.7,1,10.2V1.3c0-0.5,0.2-0.9,0.5-1.2s0.8-0.5,1.2-0.5H17
+          c0.5,0,0.9,0.2,1.2,0.5c0.3,0.3,0.5,0.8,0.5,1.2v8.9c0,0.5-0.2,0.9-0.5,1.2S17.5,12,17,12z M2.8,0.9C2.7,0.9,2.6,1,2.5,1
+          c0,0.1-0.1,0.2-0.1,0.3v8.9c0,0.1,0,0.2,0.1,0.3c0,0,0.1,0.1,0.3,0.1H17c0.1,0,0.2-0.1,0.3-0.1c0.1-0.1,0.1-0.2,0.1-0.3V1.3
+          c0-0.1,0-0.2-0.1-0.3c0,0-0.1-0.1-0.3-0.1C17,0.9,2.8,0.9,2.8,0.9z"
+              />
+            </g>
+            <g id="Line-2">
+              <path d="M19.5,14.4h-19c-0.4,0-0.7-0.3-0.7-0.7S0.1,13,0.5,13h19c0.4,0,0.7,0.3,0.7,0.7S19.9,14.4,19.5,14.4z" />
+            </g>
+          </g>
+        </g>
+      </g>
+      <g>
+        <rect
+          x="2.9"
+          y="10.3"
+          transform="matrix(0.8327 -0.5537 0.5537 0.8327 -4.0847 8.3949)"
+          width="17.9"
+          height="1.4"
+        />
+      </g>
+    </SvgIcon>
+  );
+};
+
 export const TrashBinIcon = (props: SvgIconProps) => {
   return (
     <SvgIcon {...props} viewBox="0 0 15.44 16">