Big repository reorganization

The code is divided in three crates:
- plume-common, for the ActivityPub module, and some common utils
- plume-models, for the models and database-related code
- plume, the app itself

This new organization will allow to test it more easily, but also to create other tools that only reuse a little part of
the code (for instance a Wordpress import tool, that would just use the plume-models crate)

src/routes/likes.rs

@@ -1,16 +1,15 @@
 use rocket::response::{Redirect, Flash};
 
-use activity_pub::{broadcast, inbox::Notify};
-use db_conn::DbConn;
-use models::{
+use plume_common::activity_pub::{broadcast, inbox::Notify};
+use plume_common::utils;
+use plume_models::{
     blogs::Blog,
+    db_conn::DbConn,
     likes,
     posts::Post,
     users::User
 };
 
-use utils;
-
 #[get("/~/<blog>/<slug>/like")]
 fn create(blog: String, slug: String, user: User, conn: DbConn) -> Redirect {
     let b = Blog::find_by_fqn(&*conn, blog.clone()).unwrap();