No Ticket: Handle shared URLs

[wtimme]

Introduction

With this branch, URLs can be shared with the app. This implements marcelklehr/chordreader#7, making it easy to go from a bookmark to the app.

How to test

1. Checkout the branch
2. Install the app on your device
3. Open your device' browser (e.g. Firefox) and navigate to a chord page
4. Invoke the "share" dialog and select Chord Reader 2 as a target

The app should open and the webview should be visible. The URL that was shared with the app should be loaded automatically.