[TASK] Extensionmanager: Change download icon

* Show details: import icon as download
* Distributions: change icon in button

Resolves: #63240
Releases: master
Change-Id: I92be1b2c091c01ae63dcc6d84614288dfde0329f
Reviewed-on: http://review.typo3.org/34821
Reviewed-by: Frederic Gaus <gaus@flagbit.de>
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>
Reviewed-by: Anja Leichsenring <aleichsenring@ab-softlab.de>
Tested-by: Anja Leichsenring <aleichsenring@ab-softlab.de>