Add splash screen showing license details

[jimmoores]

Replace the Win32 loading progress bar with a splash screen with a progress bar. It should display whether the product is licensed under a commercial license if a license key is present (along with who it's licensed to). If a commercial license is not present, it should indicate that and remind the user that the GPL applies to any linked code.

• [x] Interface and factory
• [x] dialog design
• [x] make text white/transparent bg
• [x] replace existing Progress class
• [x] test for license

[jimmoores]

All except license test

[jimmoores]

Done