Create Prepare_genome subworkflow

[Emeerdink]

Description
Create a subworkflow that prepares all genome files required as input for alignment and further downstream processes. This part is inspired by the nf-core/rnaseq/subworkflows/local/prepare_genome subworkflow.

Examples of output:

• Everything prepared in Step 1: Prepare Annotations of the old lncpipe pipeline (line 180)
• HISAT index (now required as input)
• STAR index (now required as input)

[Emeerdink]

Work done in Feature/prepare_genome