bugfix 4-color plot - add support for multi-line FASTA input

[owlang]

Current behavior of Four-color plot gives a row for each sequence line instead of each FASTA entry. For example,

>chr12:467688-467869(+)
TACGTATTTCTCGCCGAGAAAAACTTCAATTTAAGCTATTCTCCAAAAAT
CTTAGCGTATATTTTTTTTCCAAAGTGACAGGTGCCCCGGGTAACCCAGT
TCCTCACTATTTTTTACTGCGGAAGCGGAAGCGGAAAATACGGAAACGCG
CGGGAACATACAAAACATACAAAATATACCTT
>chr12:458617-458798(+)
TTTCCAAAGTGACAGGTGCCCCGGGTAACCCAGTTCCTCACTATTTTTTA
CTGCGGAAGCGGAAGCGGAAAATACGGAAACGCGCGGGAACATACAAAAC
ATACAAAATATACCTTTCTCACACAAGAAATATATGCTACTTGCAAAATA
TCATACCAAAAAACTTTTCACAACCGAAACCA

creates a 8-row Four-color plot instead of 2-row plot.

Fix: handle FASTA parsing so that this example would generate the 2-row plot