[rosalind] handle default and cmd line input in orf example
[rosalind] handle default and cmd line input in orf example

stmuk/perl6-examples,shlomif/perl6-examples,perl6/perl6-examples,Quinny/perl6-examples,Quinny/perl6-examples,Quinny/perl6-examples,shlomif/perl6-examples,perl6/perl6-examples,shlomif/perl6-examples,Quinny/perl6-examples,shlomif/perl6-examples,Quinny/perl6-examples,stmuk/perl6-examples,perl6/perl6-examples,stmuk/perl6-examples,shlomif/perl6-examples,perl6/perl6-examples,stmuk/perl6-examples,perl6/perl6-examples,stmuk/perl6-examples