revert to old px4 firmware#2

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macekj wants to merge 2 commits intoMAAV-Software:masterfrom

macekj:sim-docker-setup

Commits on Sep 29, 2019

revert to pulling px4 firmware from github, add temporary command to build sim
macekj
committed

Commits on Oct 6, 2019

fixed gazebo build setup, add x window support for linux
macekj
committed