[notification] Position on screen

- Add configurable position on screen for notifications.
- Add missing DocStrings.
- Update translations.
- PEP8 / Lint compliant.
- Remove hardcoded integer for duration.

![temp](https://f.cloud.github.com/assets/1189414/2428559/be55358c-ac4d-11e3-9bf0-6a0550a380f5.jpg)

Brancho: feature/notification :octopus: