Implemented conference views, still incomplete
draft: relating talks with conferences
Created talks are now associated to their conference automatically, allows the creation of several talks in series ("thanks" view)
Using conference/id/talks now returns a conference's talk list
Talk details are now accessed through 'conference/conference_id/talks/talk_id' instead of 'talks/talk_id'
Removed base 'talks/' routes
Updated migration schemas and added 'location' field to both conferences and talks
Fixed minor typo
Added seed with several conferences and talks
Adjusted condition checks
Added localization files