build-indexes/fetch_fasta.sh: update Ncrassa (current version is 11/03/13, previously 25/0
6/10).
Updated ChangeLog.
share/versions.sh: added bowtie2.
build-indexes/bowtie2_build_indexes.sh: wrapper script to build bowtie2 indexes from fasta.
build-indexes/build_indexes.sh: remove bfast index building, add bowtie2.
build-indexes: updated README.
Updated ChangeLog.