Core

Added file upload, date and author fields to blogposts, and various other PubSweet Science Blogger 0.1 additions/fixes.

See merge request !8

Datastore

Switches from a Postgres backed datastore to a LevelDB datastore, requiring no installations on the user's part. Additionally it simplifies the backend structures from "manages" and "creates" into "collections" and "fragments", exposed in a well tested REST API.

See merge request !7

This reverts commit 058a47cb.

Remove server-side rendering, as it increases complexity and makes debugging harder. We can always add it later, when things are more stable.