Camera-traps runtime configuration enhancements

[richcar58]

Consolidate all plugin runtime configuration under a single directory as shown here:

traps.toml 
log4rs.yml
plugins
    | — image_gen
    |        image_gen_config.json
    | — image_recv
    | — image_score
    | — image_store
    |        traps-image-store.toml
    | — observer
    | — power
tests
    | — rust_integration
             traps-integration.toml

Use the new CAMERA_TRAPS_ROOT environment variable or command line argument to specify the runtime configuration.