Add admin page and enable users to select languages

• Fix issue where added markers do not have id assigned, thus preventing detail view
• Add admin page
• Allow users to select a language for their session
  • After language change, app is reloaded in frontend to display new language. No resources at this point to implement more sophisticated method as babel is implemented localization framework
• Allow user to toggle between all of the markers and removal requested oes
• TODOs left
  • Filter markers
  • Fix failing test
  • Translate forms
  • Resolve main merge conflicts