Select BLAST+ 2.2.27 and 2.2.28 binaries via uname/arch specific actions.

Based on the recent change for package_blast_plus_2_2_26 which
was successfully tested on the Test Tool Shed last night.
Fix make_ncbi_blast_plus.sh, was omitting repository_dependencies.xml
Now target BLAST+ 2.2.27
Mention needs updated blast_datatypes