fix: open libraries from v9.5.0-pr1 in newer versions

[CyanVoxel]

Summary

This PR provides a critical fix for opening libraries created in v9.5.0-PR1 as well as providing improved feedback for library opening errors, adding tests for migrating from previous SQLite library versions, and adding documentation for internal database format changes.

Fixes

• Libraries created in v9.5.0-PR1 (DB_VERSION 6) can now properly be opened with the current version of the program
• The window title is no longer completely replaced by the name of the error encountered when opening a library

Additions

• The full error traceback is now provided as part of the error message given when failing to open a library
• Added test cases for opening all versions of the library database (DB_VERSION 6, 7, and 8)
• Added documentation for the history of the save file format changes

Fixes #813.

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Example of the traceback generated by #813 shown in the new message box (macOS).