[development] Move all core modules into their own directories.

[Scott White]

I think using template files is a great idea, but not at the expense of 
using other theming engines.


Neil Drumm wrote:

> Dries Buytaert wrote:
>
>> The disadvantages:
>>  * PHPTemplate would become more dominant.  It's not clear how this
>> can co-exist with other theme engines.
>
>
> I would actually be okay with removing the whole engine system and 
> simply doing PHPTemplate only. Sure theme engines are a nice feature, 
> but how many are maintained and what % of themes are PHPTemplate?
>