Add --input schema and parsing

[DarianHole]

Adding in the nf-core samplesheet validation including:

• Schema plugin
• Schema validation json
• Parsing samplesheet and combining fastq files for the same sample

PR checklist

• This comment contains a description of changes (with reason).
• Make sure your code lints (nf-core lint).
• Ensure the test suite passes (nextflow run . -profile test,docker --outdir <OUTDIR>).
• Check for unexpected warnings in debug mode (nextflow run . -profile debug,test,docker --outdir <OUTDIR>).
• Usage Documentation in docs/usage.md is updated.
• Output Documentation in docs/output.md is updated.
• README.md is updated (including new tool citations and authors/contributors).