Operator splitFasta should allow the creation of chunk having the same size

[lucacozzuto]

Splitting fasta is a trivial task but doing it in a way that every piece is more or less homogeneous will help to optimize the parallelization step. So I suggest a new parameter for this purpose.

[pditommaso]

Should the header counted to determine the chunk size? I would say no.

[lucacozzuto]

chunk size should be only referred to the sequence. Thanks!