adding cDNA generation script

solving #5

requested review from @zavolan

1. I read the transcript ID and transcript sequence from fasta-file
2. search in gtf-file for transcript ID to find all priming sites for that transcript
3. search in csv-file for transcript ID to find the count of transcript
4. create cDNAs: loop over the counts of a given transcript, select a priming site in proportion to their relative probabilities and generate the DNA that starts at the transcript start and ends at the chosen priming site 5a. write output fasta-file: cDNA ID and cDNA sequence 5b. write output csv-file: "cDNA ID, Gene ID, Count of cDNA"

closed