hacked together camera depth simulation

I got annoyed that I couldn't test our camera stack as my internet is crap and I can't download rosbags. So I hacked together a simulation of depth data. It adds even more ZED topics but at least we get proper depth simulation and it seems pretty realistic.

I tested this with the latest darknet_combined branch and it worked well.

The only caveat is that the point cloud of the camera is a fucked as it is in the wrong coordinate frames. I'd love to fix that but that would break many more things in our stack so I'm just going to leave it like this.