Add view-decorator login_required() to refactor 401 cases

[lefnire]

This creates a login_required() decorator which adds g.user and g.auth_token to flask's request globals. For your project, it simply refactors two functions' shared code into one; no biggie. But for projects which use this code, it allows them to use the same logic for all their Flask routes requiring auth. Eg:

# new file - views.py
from project.server.auth.views import login_required
from project.server import app

@app.route('/something')
@login_required
def something(): pass

[chexex]

Duplication :)
auth_token = auth_token ...