Add some additional information to loader.php

[fanquake]

Clean up the whitespace in loader.php and add the Revision date, Requires at least and License to the header.

Tested up to would also be another useful piece of information to add.

i.e Tested up to: WP 3.4.1, PHP 5.4.4, MYSQL 5.x.x

[DJPaul]

I don't have a problem with adding the License line in, but 'Requires at least' and 'Tested up to' are readme.txt headers.
I see no value in introducing a 'Revision Date' header, nor adding the PHP or MySQL versions to anywhere.

[DJPaul]

Let's put the license line into loader.php, and leave it as that.

[jkudish]

add licence to loader header

[johnjamesjacoby]

(In [6594]) Add license to bp-loader.php. Fixes #4446.