Replace IconsExt dependency with a new Icon Browser

[bmcclure]

The browser should:

• Optionally take a default icon source to pre-select
• Allow browsing the filesystem for a .ico or .exe file, or choosing from a list of free game-oriented icons
• If a .exe is chosen, show an additional browser that lets you choose between the icons in the .exe if there is more than one
• Store a main reference to the source that is selected and return it at the end
• Optionally extract the chosen icon to a destination