Qt: ampersands in ruleset/user text can cause unwanted mnemonics
There are a number of places where the '&' (ampersand) character in ruleset- or user-defined text is not escaped, and can cause unwanted mnemonics to appear in Qt menus and buttons.
One example is the nation 'J&W' in the alien ruleset; on the start screen, if that nation is selected, then the pick-nation button becomes 'J_W_' (crude rendering).
The '&' character is a reasonable thing for a ruleset, city name, etc to contain.
is_allowed_city_name() allows it at its most strict (and Cut & Shoot, Tyne & Wear, etc are not implausible place names).
This affects menus (where they mention extras, governments, actions, etc); action choice dialogs; the "pick nation" button; and the "rename city" button.