Make offline presence to stop sync

Setting the presence of an account to offline
will make the client to end sync task and will
prevent messages from being sent.

Setting it to online again or any other presence
will start sync task again.

Left:
- Local echo to presence change
- UI Control to affect all members presence
- Block more requests to be sent (e.g. member
  actions)

src/gui/MainPane/AccountContextMenu.qml

@@ -12,18 +12,16 @@ HMenu {
     property string userId
     property string presence
     property string statusMsg
-    property bool   firstSyncDone
 
     onOpened: statusText.forceActiveFocus()
 
 
-    function setPresence(presence, statusMsg = null) {
+    function setPresence(presence, statusMsg = undefined) {
         py.callClientCoro(userId, "set_presence", [presence, statusMsg])
     }
 
 
     HMenuItem {
-        enabled: firstSyncDone
         icon.name: "presence"
         icon.color: theme.controls.presence.online
         text: qsTr("Online")
@@ -31,8 +29,7 @@ HMenu {
     }
 
     HMenuItem {
-        visible: presence
-        enabled: firstSyncDone
+        enabled: presence
         icon.name: "presence-busy"
         icon.color: theme.controls.presence.unavailable
         text: qsTr("Unavailable")
@@ -40,7 +37,6 @@ HMenu {
     }
 
     HMenuItem {
-        enabled: firstSyncDone
         icon.name: "presence-offline"
         icon.color: theme.controls.presence.offline
         text: qsTr("Offline")
@@ -48,8 +44,7 @@ HMenu {
     }
 
     HMenuItem {
-        visible: presence
-        enabled: firstSyncDone
+        enabled: presence
         icon.name: "presence-invisible"
         icon.color: theme.controls.presence.offline
         text: qsTr("Invisible")
@@ -60,8 +55,7 @@ HMenu {
 
     HLabeledItem {
         id: statusMsgLabel
-        visible: presence
-        enabled: firstSyncDone
+        enabled: presence && presence !== "offline"
         width: parent.width
         height: visible ? implicitHeight : 0
         label.text: qsTr("Status message:")
@@ -80,12 +74,14 @@ HMenu {
                 }
 
                 defaultText: statusMsg
+                placeholderText: ! presence ? "Unsupported server" : ""
 
                 Layout.fillWidth: true
             }
 
             HButton {
                 id: button
+                visible: presence
 
                 icon.name: "apply"
                 icon.color: theme.colors.positiveBackground