Fix compute-accuracy

Fix the compute-accuracy sub-command to actually compute accuracies rather than analogies.

Single binary

• finalfusion-utils has been converted to a single binary with subcommands.
• The finalfusion completions subcommand can be used to generate shell completions.
• Switch to finalfusion 0.10 and reductive 0.3.

Lossy conversions

Add the --lossy option to ff-convert. This support conversion of text/word2vec/fastText embeddings with tokens that contain malformed UTF-8.

Support for fastText embeddings

• Add support for reading and converting fastText embeddings.
• ff-compute-accuracy: report average cosine similarity for analogies.
• ff-{analogy,similar}: report words with failed embedding computation