Since there are currently a lot of error coded returning 1, that mean
completly different thing, i guess it would be very nice to change this.
A client should not be forced to parse the error message, the error code
should be enough to explain the error.

This change suggests some error codes, that have a hierarchical
structure. In the following list the categories begin with = and the
error codes actually used with -.

= 100 	Page errors
== 110	Page access errors
--- 111	User is not allowed to read the requested page
--- 112	User is not allowed to edit the page
== 120	Page existance errors
--- 121	The requested page does not exist
== 130 	Page edit errors
--- 131	Empty page id
--- 132	Empty page content
--- 133	Page is locked
--- 134	Positive wordblock check

= 200 	Media errors
== 210	Media access errors
--- 211	User is not allowed to read media
---	215	User is not allowed to list media
== 220	Media existance errors
--- 221	The requested media does not exist

= 300	Search errors
== 310	Argument errors
--- 311	The provided value is not a valid timestamp
== 320	Search result errors
--- 321	No chances in specified timeframe

Without creating an IXR_Base64 object, the file will be encoded as base64, but send as string. The client XML-RPC parser cannot detect that it is meant to be a base64 encoded file.

The login wasn't able to modify the session as it was already closed
earlier.

This patch also executes the correct event when logins via XMLRPC are
done.

If the user is already logged in, a 403 is sent instead now.

This is far from perfect but should solve most issues in the recommended
configuration where only authorized users have access. Sending proper
status codes should be implemented when the API implementation
refactoring is done.

This reverts commit ba6c070e.
This reverts commit 92351008.

jquerized

  * Fix selector in subtree loading callback
  * Remove HTML inconsistencies between AJAX and plain PHP lists
  * Unify icon and CSS class switching in dw_tree and dw_mediamanager

Make it faster, prettier, less wrong, add UI effects, use jQuery UI Dialog,
Abstract tree view stuff away into jQuery.dw_tree

There are probably more functions that should go in here