Banning ampersand (&) in install path overly restrictive

Ampersand (&) is included in a list of "ambiguousChars" in packagemanagergui.cpp. I cannot find any documentation justifying its inclusion (or indeed explaining what "ambiguous" means in this context).

As far as I'm aware, windows does not restrict the use of ampersands in filenames.

Unfortunately, the most common location for software to be installed on windows is in "C:\Program Files\<Company Name>\<Product Name>", and it is quite common for companies to have ampersands in their names. This means that Qt Installer Framework is awkward or unusable for many companies.

Other installer frameworks do allow ampersands.