[BUGFIX] Page module: Allow to paste in empty columns

Since quite a long time it was not possible to paste a content
element into an empty column of the page module. This patch
introduces an icon in the top right corner of each column if
a tt_content element is on the clipboard (Default pad). When
the icon gets clicked the content elements from the clipboard
get moved/copied into the selected column/language.

As a side effect this patch also resolves issues with the list
module not reloading when using the copy/cut entries from the
clickmenu (context menu): #25176, #15958

Change-Id: I635bb584d5e03b764bd5df5189555fb9b34ab926
Resolves: #44002
Resolves: #35980
Resolves: #15080
Resolves: #21622
Resolves: #25176
Resolves: #15958
Releases: 6.1, 6.2
Reviewed-on: https://review.typo3.org/25521
Reviewed-by: Markus Klein
Tested-by: Markus Klein