Cherry-pick of "Merge branch 'ThreadsUpdate-1.0-20180208' into '1.0'" into master

FindThreads Update, 1.0 branch (2018.02.08.)

See merge request !232 (merged)

(cherry picked from commit 72c40ada)

• 6ebf2226 Switched the FindBoost.cmake module to use the Threads::Threads
• d5392fdf All projects are now setting THREADS_PREFER_PTHREAD_FLAG for their
• 4299335b Turns out that Gaudi (at least v27) gets freaked out by imported interface