[boost] [GSOC19] Congrats to all students and mentors

Hi, GSOC finished for 2019. We had 11 students this year and all of them survived the summer and contributed a lot of good stuff. Hopefully, most of it will be merged in the next few weeks. Thanks to all students and mentors, and to Boost community for supporting the program. Special thanks to David Bellot that worked as org admin and dealed with the logistics in addition to mentor. Cheers, Damian