Better error handling

[bepoli]

The program should raise errors in case something in the input files is wrong, avoiding crashing with uninformative messages such as those dealt with in #1. Keeping here a list of errors/exceptions to implement:

• [x] requirement not met (error if not present, warning if version is not supported)
• [x] cell barcode and UMI tags not found in BAM
  • [might check for header if STARsolo attributes are not included (https://github.com/bodegalab/irescue/issues/1#issuecomment-1431680110)
• [x] BAM reference names not matching with BED
• [x] couldn't download the annotation data for a genome assembly (for any reason)