[TASK] Better sorting for results of EM

If a search expression matches an extension key, the result
should be listed at the 1st place.

For example searching for "templavoila" or "news" should have
the templavoila extension or news extension at the 1st place
and not on a random one.

Change-Id: Ib0abb290b810b903d9e277935f81d88cadc18f8a
Resolves: #31143
Releases: 4.6
Reviewed-on: http://review.typo3.org/6134
Reviewed-by: Philipp Gampe
Tested-by: Philipp Gampe
Reviewed-by: Oliver Hader
Reviewed-by: Xavier Perseguers
Tested-by: Xavier Perseguers