Fix Sytem Tray Menu behaviors

This are still adjustments to fix before releasing. Testing environment: macOS and GNU/Linux.

1. When there is no account, the systray menu has 2 entries. The quit entry does not work:

Systray.qml:379: TypeError: Property 'hide' of object Systray_QMLTYPE_124(0x7f812ae9eaf0) is not a function

2. Into the Account details, when you select the other UI, the choice is not taken into account in the systray menu. For instance :

• select the other UI (if you are using JSF, change to Web-UI)
• click into the server link icon in the systray menu to open the browser pointing at the server URL
• it should use the selected UI

3. Systray sub-menu should be invisible:

• click on the systray submenu
• click elsewhere, outside the systray menu
• the menu is now closed
• click on the systray icon to show menu
• the submenu is opened

4. The Items to sync: xx sentence seems broken. If there are 100 items, it displays only "10".

5. The systray menu is not refreshed when data is updated (sync items, conflicts button appearace). These should be updated in alsmost real time (check the remaining files to sync, be able to show the conflicts/errors window when one file is in error).

6. The conflicts window is not correctly updated upon action.