Gym environment for PLOW (7th edition)

• ARGoS3 side, with xml file, cpp controller, loop
• Generic gym env for argos3
• gym env for crossroads (this repo)
• Learning algorithm, developped using the chi framework for tensorflow

All 4 repos must be at the same level, in the same directory

Juliette Tibayrenc Winning team of the PLOW challenge: Anthony Dentinger, Jayant Harilela & Emir Khaled Belhaddad [see 518cb978]

Thanks to Simon Ramstedt for the general code structure