Various fixes

Fixed queries with "RETURNING ID"
Added id and username to session variables on login
Added foreign key restrictions to schema.sql
Fixed user signup
Merge origin/master

Conflicts:
	src/main/java/theworldnews/database/news/objects/Article.java
	src/main/java/theworldnews/database/news/queries/DisplayQueries.java
	src/main/java/theworldnews/database/news/queries/latest.java