PARIS — French-German tank builder KNDS plans to list its shares on the Paris and Frankfurt stock markets in an operation that will see existing shareholders selling about 20% of the company to institutional investors and Germany buying a 40% share. The two holding companies that currently control KNDS, French state-owned Giat Industries and German family-owned Wegmann & Co, will together sell about 20% of the company, KNDS said in a statement on Wednesday. The Federal Republic of Germany