CBD-935:  move logic from show_latest_build.cgi to new buildbotReports.pm,

with methods: last_done_build (builder, branch ),  which returns ( status, iteration, build_num, build_date )
              last_good_build (builder, branch ),  which returns ( iteration, build_num, build_date )

Change-Id: I465e689d6c04755105a9630dc83e2ef0e1faa10b
CBD-935:  fix changelog report generation and output

Change-Id: Ie924009beb0171af6d42d351cd4ea0880b90e77d