Implement sending logs to developer (#190)

* Save logs to a file

* Send logs via email

* Enable network logs in release builds

* Remove useless chooser title

* Append to logs file and ignore I/O errors

* Ensure email and password are not logged

* Ensure base URL is never logged

* Add logs disclaimer

app/src/main/res/xml/file_provider_paths.xml

@@ -0,0 +1,6 @@
+<?xml version="1.0" encoding="utf-8"?>
+<paths>
+    <files-path
+        path="."
+        name="log.txt" />
+</paths>