* Enable nullable reference types where possible.
This enables C# 8 nullable reference types. Many files have nullables disabled so I don't have to fix everything at once. I'll get them all enabled bit by bit. All new files default to nullable now.
* Preparing for implementation of gradients.
* Make LottieGenCorpus more deterministic.
Previously the output depended on the width of the console, and sorting ignored case.
* Upgrading to SDK 18362 (May 2019) so that we can use RadialGradientBrush.
aborziak-ms
Alexandre Zollinger Chohfi
Simeon
Simeon