Allow indenting/tabbing in the plugin/theme editors

[nacin]

Since the file editors aren't going anywhere, we should encourage those using it to at least write better(-looking) code by allowing them to easily intent said code.

Enter Tabby (​http://plugins.jquery.com/project/TextareaTabs), a jQuery plugin that I've been testing locally and seems to work really well.

It allows for Tab and Shift-Tab (outdenting) and multi-line tabbing.

Patch coming.

[nacin]

(In [13131]) Allow tab intents in plugin/theme editors. Utilizes the Tabby jQuery plugin, see #12204

[azaozz]

Don't think we need yet another external JS file (and the maintenance/support that comes with it) just for typing tabs in textareas. Also this plugin doesn't add support for the tab key, it uses it as a one key shortcut to indent/outdent text blocks which is different from most text editors and unexpected for most users.

Pros:

• somehow buggy support for tabs in textareas.

Cons:

• yet another external file to maintain.
• far too large at 10KB (the needed code is about 700 bytes).
• buggy in IE6
• sometimes adds empty lines and/or spaces

Think we will be better off with a small function that "types" tab in the themes and plugins editors textareas.

[nacin]

Thanks for the review, I've tested it a bit further and saw the flaws you mentioned. Jumped the gun a bit, my first thought was to assign it to you and I skipped that.

12204-2.patch​ looks good, tests fine. I'll revert [13131] and check that in tomorrow.

[nacin]

(In [13191]) Allow tab to intent in plugin/theme editors. Reverts first pass, [13131]. Props azaozz, fixes #12204