add_plasmid: add_plasmid
In alex-kalinka-cruk/fgcMetadata: FGC CRISPR Metadata system

Adds a plasmid experiment to an analysis in an object of class fgcMeta, as produced by fgcMetadata::start_fgc_project.

1	add_plasmid(meta, name, indices, slx_id, counts_file, description = NA)

`meta`	An object of class `fgcMeta`, as produced by `fgcMetadata::start_fgc_project`.
`name`	A plasmid sample name.
`indices`	A character string naming the indices, e.g. 'i701-i502'. Can be `NA`.
`slx_id`	The SLX ID. Can be `NA` if `counts_file` is not `NA`.
`counts_file`	A name for the counts file. Can be `NA` if `slx_id` is not `NA`.
`description`	A description of the plasmid. Defaults to `NA`.