[FEATURE] Use internal link generation for usernames

The Twitter api provides information according to mentioned users in a
tweet. Those usernames are wrapped with a link to their Twitter profile
within internal tweet handling.

Change-Id: Ie72210561696f46d024d5f8a0d3cac8ae301eaef
Reviewed-on: https://review.typo3.org/26742
Reviewed-by: Nicole Cordes
Tested-by: Nicole Cordes