System for user accounts

[jkokocha]

At the time of writing this, there is no real reason to implement this, but it might be an interesting idea for the future. The idea is simply to have a registration and log in feature for users connected to a database. This opens up for many future opportunities such as:

• Users being able to create their own content pages, like a forum (Issue Users being able to create their own content pages #31)
• A chat/comments system
• Users being able to track their personal learning progress. (Issue Progress bar for how much users have learned #34)