Fix updating of sequence dictionary.

Picard Tools will re-use an existing sequence dictionary, when
CreateSequenceDict is used, which means that the tool will fail
if the underlying FASTA has changed. This works around that
behavior by creating a symbolic link in temp folder to the FASTA.
Fix merging by label in .summary files.

Previously, only the size of the one prefix would be used, if multiple
prefixes had the same label. Furthermore, all prefixes with that label
would be identical in the table of genomes. This corrects this behavior
so that the total size is used, and that the individual stats are shown
in the genomes table.