correct yt link

Docker improvements

- Run onionr by default rather than bash
- Run as unprivileged user by default instead of root
- Use /app for all code
- Specify python 3.7 (3.8 fails to build cffi)
- Use apt-get rather than apt (apt's CLI is not stable)
- Slight reformatting and consolidation

Added custom port and bind address args

tests/test_default_config_json.py

@@ -24,6 +24,7 @@ class OnionrConfig(unittest.TestCase):
             self.assertEqual(conf['allocations']['disk'], 1073741824)
             self.assertEqual(conf['allocations']['disk'], 1073741824)
             self.assertEqual(conf['general']['announce_node'], True)
+            self.assertEqual(conf['general']['bind_address'], '')
             self.assertEqual(conf['general']['dev_mode'], False)
             self.assertEqual(conf['general']['display_header'], True)
             self.assertEqual(conf['general']['ephemeral_tunnels'], False)