dolphin: Show full file info in statusbar when only one file is selected

The purpose of this change is to give the user a chance to see hover
file information if it doesn't fit in the status bar, by allowing to
click on the file and hover on the status bar.

As it's now possible to have status bar texts starting with "<qt>",
DolphinPart::updateStatusBar() must escape strings. Otherwise,
filenames such as "<qt>Tes<font color=red>t" would be rendered as HTML
data in konqueror's status bar when selected.

BUG: 260717
FIXED-IN: 4.12.0
REVIEW: 111934