Android fixes (#515)

* Fix profile screen performance on android and remove dead code

* Correctly handle android hardware back btn

* Fix EditProfile modal for android

* Fix lint

src/lib/routes/back-handler.ts

@@ -0,0 +1,11 @@
+import {BackHandler} from 'react-native'
+import {RootStoreModel} from 'state/index'
+
+export function onBack(cb: () => boolean): () => void {
+  const subscription = BackHandler.addEventListener('hardwareBackPress', cb)
+  return () => subscription.remove()
+}
+
+export function init(store: RootStoreModel) {
+  onBack(() => store.shell.closeAnyActiveElement())
+}