LT-15571: Update SIL Logo (80th Anniversary)

Use the new SIL + 80th Anniversary logo throughout FLEx, including:
- SplashScreen and Help > About (dialog and icon)
- A few other places that I'm not exactly sure what they do
I'm pretty sure I got everything.  See screenshots in Jira.

Change-Id: I77e2a277652a9ee7beb122b439aaad9e6749b695