BDD: add profiles plus needed steps and implementation for setupwizard

Added profiles: ```installdemocontent``` ```installdemoclean```

Added needed steps/functions for the Setup Wizard test see https://github.com/ezsystems/ezpublish-kernel/pull/783 for more detais

Tasks:
- [x] Add profile for demo installation with/without content 
- [x] Needed steps (and helpers) for installation process 
- [x] Change travis setup so it **do not** make installation
- [x] Change travis script so that it start through installation and then democontent
- [x] Change mink driver from Sahi to Selenium2