Resolve "Fixed minor internationalization things"

Related to #5 (closed)

While I was working on our SaaS website at https://baserow.io, which installs Baserow as a depedency, I noticed that a couple of things were not working because of some internationalization changes. I decided to create a merge request with some fixes.

What has changed

• Because the web-frontend Registerable class now always expect the app parameter, I decided to make it consistent and always provide it when initializing every instance.
• Fixed passing along the args, which contains the context when calling super.
• Replaced the relative locales path with an absolute one because it could result in problems when using Baserow as depedency.