BankFile: Seemingly functional checksum implementation. ProjectFile: Handle missing file keys more cleanly/obviously. ProjectFile: Handle non utf8 characters in project datafiles. ProjectFile: Add a method to check a project's os version compatability against the library. ProjectFile: Fixup: reading slots created an owned PathBuf instance for branch condition. ProjectFile: Add test cases for parsing non-utf-8 sample file paths. ArrangementFile: Fixup: Unwrap would always error as unwrapping a None. Lib: Add array of allowed OS version strings for the library.