**Only one functional change**
* Fixes a bug in LogFactory where `Warning` is being logged as `Information`
Non-functional changes:
* Updates/Fixes copyright headers
* Removes namespace scopes for core files.
View with [whitespace off](https://github.com/modernuo/ModernUO/pull/1187/files?w=1).
* Introduces `RawInterpolatedStringHandler` which is exactly the same as `DefaultInterpolatedStringHandler` except it _unsafely exposes_ it's `ReadOnlySpan<char>` buffer. This is useful for writing the string's data without actually building the string.
* Uses this new string interpolation handler in `SpanWriter` to eliminate intermediate strings built. This is immensely useful in eliminating string allocations in writing Gump packets.
