Add database schema as a migration

[eablokker]

The database schema is included as an .sql file. Would be great if we also had it as a migration that uses the db forge to build the schema. Might make it easier to deploy, and integrate better with apps that are developed using migrations.

[StorytellerCZ]

I guess this is for the 2.x branch. I was thinking of doing this but first I want to finalize all the features and make sure they work fine. But if you want to go ahead and start building it, please do, because its going to be a while before I get to it.