[TASK] Integrate collection selection behavior in workspace module

Since TYPO3 6.2 parent-child structures are visualized in
the workspace module. However, this representation lacks
the possibility to select all elements of that accordant
collection by one click.

A new event "holdclick" is integrated that is fired after
holding the mousedown event for 400ms. This event then
leads to have all records of the collection selected.

The regular mousedown (click) behavior still stays the same.

Resolves: #60010
Releases: 6.2, 6.3
Change-Id: I98d26f125428446157294866484f8be7106b0c51