Remove the server side session storage and store all the session related data
in the client side cookies. This decreases the exposure of the auth tokens.
It also simplifies the installation process as bloat no longer requires write
access to the filesystem.

This is a breaking change, all the existing sessions will stop working.

There's only one flag, so it doesn't matter.

- Remove separate auth/logging and merge them into transport.go
- Add helper function for http handlers