Elodie with Manifest

Changes from jmathai/elodie:

• Important: run Exfitool in batch mode rather than once per file, to mitigate significant fork overhead on Windows
• config file is json rather than ini, and can be read from anywhere, and is required
• target file naming convention changed
• Attribute 'origin' added
• Attributes (currently only origin) can be specified by a prefixed directory name: origin$whatever
• 'Db' renamed to manifest
• manifest is still written as json but each file hash has nested attributes rather than being a simple source -> destination pair. This is to (eventually) allow multiple sources and targets for each file.

The intent of many of these changes was to:

• Enable copying to multiple targets from multiple sources, including cloud targets
• Match my file naming convention to be able to filter out undated photos (ie gifs/screenshots) while