BDD: Add new start page scenarios

Adding new BDD to start page feature.

Depends and it's needed by:
> ezsystems/ezpublish-community#131
Since the ezsystems/ezpublish-community#131 changes the page mapping to lower case, tests wont pass until, changing that on demo also (setup wizard is already merged)

- [x] Update start page feature file
- [x] Move start page feature file to DemoContent folder
- [x] Move content stuff in the feature context to content context (keep all regarding content on the content context)
- [x] ~~Update contexts files to implement internal interfaces~~
- [x] Update travis to use the scripts on community (PR:#71)
- [ ] Merge sentences in browser context (ezsystems/ezpublish-community#131)