[scheme designer] Fix for 1690, 1691, 1692

- Fix for #1690
- Fix for #1691
- Fix for #1692
- Use translations.
- Update translations.
- Add missing DocStrings.
- PEP8 / Lint compliant.
- Group Widgets on a QGroupbox for better placements.
- Add Placeholder Text.
- Add quick Preview Area QGroupbox.


![temp](https://cloud.githubusercontent.com/assets/1189414/2719119/4207c6b2-c55b-11e3-8041-68ad25767541.jpg)


Brancho:  fix/scheme_designer  :octocat: