GitLab

This makes a few adjustments that are necessary for Swift 5.2 and Xcode 11.4 - especially for SPM

- Symlink workaround now produces a warning -> move headers into subfolder, change to fully qualified imports and remove symlinks
- Cleanup Header import order - errors first, then 3rd party, then ours
- Update Package.swift for Swift 5.2
- Fix gitignore to not ignore our Lumberjack.xcodeproj