MDL-43842: Import atto back into core
MDL-43842 Atto: Move pix-icons into core pix folder.
MDL-43842 Atto: Remove licence and README.txt
MDL-43853 Atto: Performance. Turbocharge the loader.

Rewrite the atto plugin loader so that:

A) We have a real settings.php page and can edit the toolbar.
B) All plugins are loaded at the same time (not serially)
C) All plugins share the YUI sandbox (more performance boost).

I had to change the loading API for this - but there are not non-core uses yet,
this is the best time to break it.
MDL-43869 Atto: id escaping so Atto works with when there is : in the id.

(Quiz)
Also includes fixes for Atto when the repositories should not be displayed.
MDL-43857: Auto clean tag bloat from word/openoffice/googledocs

The cleanup rules are pulled from both testing of live docs, and the
jquery clean plugin. I tested with googledocs, libreoffice, word 2003
and word 2013.
MDL-43950 editor_atto: Add arguments to plugin callback params_for_js
MDL-43869 Atto: Add functions to get the nodes from the elementids.

If plugins try and do this themselves with Y.one, they will fall foul of the
qtype essay page bug which uses : in the id for form elements.

This is an alternative solution, to escaping the ids, which seemed unreliable for older
version of ie.
MDL-43858 atto_charmap: New plugin to insert special characters
MDL-43869 Atto: Fix broken repositories.

The previous change on this issue accidentally fixed a selector,
so the repository API was recieving a valid node instead of null.
This means that it calls it's undocumented and dodgy callbacks on the node,
which are really calls directly to the TinyMCE API (just well buried).

But - by not setting the editor_target property, the api will not do
the secret handshakes.
MDL-43859 atto_smiley: New plugin to insert smileys
MDL-43862 atto_managefiles: New plugin to manage files

AMOS BEGIN
 CPY [hasmissingfiles,tinymce_managefiles],[hasmissingfiles,atto_managefiles]
 CPY [deleteselected,tinymce_managefiles],[deleteselected,atto_managefiles]
 CPY [unusedfilesdesc,tinymce_managefiles],[unusedfilesdesc,atto_managefiles]
 CPY [unusedfilesheader,tinymce_managefiles],[unusedfilesheader,atto_managefiles]
AMOS END
MDL-44003 editor_atto: Identify the submit buttons in plugins
MDL-44003 Atto: Set type="button" on atto toolbar buttons.

To prevent them accidentally becoming the default submit buttons for the form.
MDL-43861: Atto Plugins: create new plugin for font and background colors
MDL-43861 Atto: Fix for toolbar menu repaint bug in chrome.
MDL-43990 Atto: Add a function for changing the formatting of the selected block.
MDL-44064 editor_atto: Do not die when a plugin is missing
MDL-43968 editor_atto: Copying latest TinyMCE icons to core pix/e
MDL-43953 editor_atto: Trigger form change when editing content