Ont-fast5-api

Fixed
- Compression argument in `fast5_subset` and `single_to_multi` failed if not set

Fixed
- Compression argument in `fast5_subset` and `single_to_multi` was parsed incorrectly

Fixed
- Argument list for `fast5_subset` and `single_to_multi` had a syntax error

Added
- Hardlinking of metadata to prevent duplication and reduce filesize
- Ability to enable compression when using `fast5_subset` and `single_to_multi`
Fixed
- `fast5_subset` thread pool could sometimes close before all tasks were completed
- `fast5_subset` will create output directory if it doesn't exist

Fixed
- Comparison of file_versions could throw an error

Fixed
- Basecall1DTools could not load data from a Fast5Read