File processing refactor and Booklore upload support (#474)

- Added new book output option **upload to Booklore**, available in
download settings
- Got annoyed at my messy processing code while implementing Booklore so
refactored the whole thing
- Full black box file processing testing with randomised configuration
- Deluge: Connect via WebUI auth for simplified setup
- Added env vars documentation, auto generated via script, and unlocked
most settings to be used as env vars

docs/configuration.md

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+# Configuration
+
+TODO

docs/dev/index.md

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+# Developer Documentation
+
+TODO

docs/index.md

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+# Shelfmark Documentation
+
+TODO

docs/installation.md

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+# Installation
+
+TODO

docs/troubleshooting.md

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+# Troubleshooting
+
+TODO