Disable multi-touch

[plplmax]

Multi-touch introduces ways to broke the app.

For example, user is opening ModalNavigationDrawer and, keeping the first finger, tap on the "Sign out" button using the second finger. ModalNavigationDrawer should be closed, but it stays open. Yeah, it can be fixed by removing ModalNavigationDrawer from UI hierarchy instead of disabling ModalNavigationDrawer's gestures, but it's redundant over-engineering.

Another example is deleting multiple notifications using five fingers simultaneously. It may be a problem in the future when implementing undo feature.