Redirect to login page if the user is not logged in.
Fixes #177
Fix view bug with "Order #"

As discussed in https://github.com/spree/spree/issues/4792, `Spree.t(:order_number)` is actually meant to take a `:number` variable, but to generate the string 'Order #' (with the hash sign) we use `Spree.t(:order_num)` instead.
mandate spacing in user_sessions/new

Spacing would sometimes be inconsistent in this line, with the newline rendering at times as a space, and at times not. A nonbreaking space will resolve this.

Fixes #200
mandate spacing in user_registrations/new

Related to #200

Fixes #201
Fix bug where @spree_user is not being set before re-displaying password edit form on blank password

Fixes #199
Fixes #198