Description

In order to fix #332 we are persisting user enable/disable notification option on localstorage.

How to test?

1. Run matrix on augusto/save-notification-option-localstorage branch.

• Notifications should be disabled by default.
• notification-disabled key shouldn't exists on localstorage.

2. Enable notifications.
   Enable notifications by clicking on NotificationCheckbox component.

• notification-disabled key should be created on localstorage with false value.

• TOGGLE_NOTIFICATION should be dispatched and systemSettings.notificationDisabled property should be updated to false on redux store.
• NotificationCheckbox component should let user disable notifications.

3. Disable notifications

• Users should be able to disable notifications again from another tab or inside a room

Expected behavior

Now matrix will save user notifications option. It will not being necessary enable and disable it every time that page is refreshed or application accessed.