Clean up code

Two things to look for in cleaning the code up:

1. Look for places code can be generalised by looking for duplicates. The make dupl command can spot duplicate code blocks.

2. Review the this, folder and storage modules. The bits of the session that are stored in this should become a Session struct in storage. Then copy most of the folder storage routines to the storage module. Just keep data verification and manipulation routines in folders.

   On this.Start (lose the This) assign the storage.Session object and then the higher level folders routines can use that (there was a cycle in the current layout when storage tried to use this.

The end result of these changes would yield easier to read/understand code. And it makes the folders module much clearer. Though moving the verification stuff from folders and users to verify? But then a routine for creating a quoted message might not fit there... Hm.