[BUGFIX] Use Sprite Icon for new Template Button

The icon in the docheader of
the Template module shows
a "create new extension template"
button which is not done via
SpriteIcon but with an old image.

This is now replaced via a Sprite Icon
and an anchor instead of a button.

Resolves: #63309
Releases: master
Change-Id: I3cae9f6454a785572e8cf51f66bfbb77b611951e
Reviewed-on: http://review.typo3.org/34580
Reviewed-by: Wouter Wolters <typo3@wouterwolters.nl>
Tested-by: Wouter Wolters <typo3@wouterwolters.nl>
Reviewed-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Tested-by: Andreas Fernandez <a.fernandez@scripting-base.de>
Reviewed-by: Benjamin Mack <benni@typo3.org>
Tested-by: Benjamin Mack <benni@typo3.org>