Hide summary file actions when a selected file does not match

When several files are selected and one of them can not be deleted the
"Delete" file action is not shown in the summary. This commit extends
that behaviour too to the other file actions in the summary ("Move or
copy" and "Download"), so now an action is shown in the summary only if
it can be executed on all the currently selected files.

Signed-off-by: Daniel Calviño Sánchez <danxuliu@gmail.com>