Logging tool and moved "About App Info" into preferences

- https://github.com/owncloud/android/issues/57
moved "About App Info" into preferences

- https://github.com/owncloud/android/issues/97
This wraps the android.util.logging into Log_OC which , if its enabled …
in the app, logs the logcat into a file. It also includes the phone
information (MODEL, VERSION...)