Update src/core/command.c, src/core/command_def.h, src/core/command_list.h files
Added option to choose the prefix added to sequence names for the following commands:
- seqcrop
- seqfind_cosme
- seqfind_cosme_cfa
- seqmtf
- seqsplit_cfa
- seqsubsky
- preprocess
- register Updates to help and definitions. Hope it's in the right place now...