* cli_args: Add --duplicate-check-hash-function.
* server.py: compare_image_hash configurable hash function
Uses an argument added in cli_args to specify the type of hashing to default to for duplicate hash checking. Uses an `eval()` to identify the specific hashlib class to utilize, but ultimately safely operates because we have specific options and only those options/choices in the arg parser. So we don't have any unsafe input there.
* Add hasher() to node_helpers
* hashlib selection moved to node_helpers
* default-hashing-function instead of dupe checking hasher
This makes a default-hashing-function option instead of previous selected option.
* Use args.default_hashing_function
* Use safer handling for node_helpers.hasher()
Uses a safer handling method than `eval` to evaluate default hashing function.
* Stray parentheses are evil.
* Indentation fix.
Somehow when I hit save I didn't notice I missed a space to make indentation work proper. Oops!