Clicking on thumbnail will enlarge it in-place instead of scrollTo in file manager

[nickvergessen]

Copied from owncloud/activity#527 by @vector090

[Andreas-Kainz]

and when you have the right detail sidebar for the selected activity? there is an preview and you have all the other file options.

could be an issue for every activity that didn't support the sidebar

[joshtrichards]

Added in #1398
Also basically a duplicate of #672