List of cores only shows most recent version

Any time DSLM should show a list of available cores, it only shows the latest version.

The issue appears to lie in the preg_match() function when sorting cores. The resulting matches array appears like this:

Array
(
    [0] => drupal-7.24
    [1] => drupal-7.24
    [2] => drupal
    [3] => 7.24
)

And the array of versions to sort is using the key `[2]` when it should be using `[3]`

The attached patch should fix the issue.