feat(startpagefallbacks): Changed the url of the home button
feat(startpagefallbacks): Settings-Object has now also the property startPage
feat(startpagesfallback): Changes in pagesservice and gitconnetctrl

- pagesservice has now a method to find one of the possible startpages
 index, home or readme
- gitconnectctrl calls now the pageservice.findStartpage function to
  check if a startpage exists and saves it in the local config settings
feat(startpagesfallback): ContentCtrl uses now the startPage
from the saved settings when no routeparam was given

Closes #45
Merge pull request #46 from mdwiki/feature/StartPageFallbacks

StartPageFallbacks: Fix the problem when the user has no index.md as startpage. Search also for the home.md or the readme.md (in this order).