Add option to leave files where they are while importing library

[T4g1]

Summary

• Fix [Feature Request] option for keep local files while library import from root folder #494

Changes

Added

• Ability to add root folders while selecting the root folder from which we want to import files
• Ability to leave files in place when importing library
• Ability to set the desired monitoring for audiobooks added through library importation

Testing

• Check that the import does not change anything in the files when it is not asked to modify them

Notes

Next steps

• [Feature Request] Allow to rename files to match the configured patterns #504 : It should be possible to process the imported files to rename them using the pattern defined in the settings. Some tests for that should be added too (see InteractiveManualImport_DontMoveAnything_DontRenameAnything)