Allow BottomNavigation with no badges on icons

[leoparis89]

Enables the use of BottomNavigation with no badges.
In the present state, is you put an empty string for a badge like this:

{ "key": "account", "title": "account", "icon": "credit-card", "color": "blue", "badge": "", "accessibilityLabel": "myLabel", "testID": "myId", } 

You get this unwanted behavior:

Now you can just do

{ "key": "account", "title": "account", "icon": "credit-card", "color": "blue", "badge": None, "accessibilityLabel": "myLabel", "testID": "myId", } 

 { "key": "account", "title": "account", "icon": "credit-card", "color": "blue", "badge": Some("33"), "accessibilityLabel": "cool", "testID": "myid", } 

Also put option type on the other non mandatory route props.