Properly (un)escape option value in case of " and ' and \

It is implemented in [] for the vlc core part but need to be stressed a bit. The interfaces (at least QT) should be modified to properly escape the strings.

added Component::Interface: other plugins label

I need more verbose :D

changed milestone to %Features paradize

The main problem is trying (and somewhat failing) to merge the list of options from a strings list to a single string. This should never happen; the interface should keep a !QStringList all the way to the input_item_t without any conversion.

added Component::Interface: Qt label and removed Component::Interface: other plugins label

But there are no good widgets to do QStringList edition.

mentioned in issue #5156