Add support from Hokuyo lidar

[mgagvani]

• Part in lidar.py to interface with Hokuyo
• Fixes to LidarPlot2 to be used with Hokuyo so it can act as a Camera in the web interface
• Integration of LidarPlot2 with existing templates/configs

Notes:
To set it up you need to configure the Ethernet port on the Pi by creating a file in /etc/interfaces.d. This is well-described by many online tutorials, and googling "f1tenth hokuyo" also brings up a lot of helpful info.

Also, unlike the RPLidar(2) parts, instead of returning a generator of individual measurements this part returns the entire scan at once. Thus in complete.py it is called lidar/dist_scan instead of lidar/dist_array.

Pictures:

[Ezward]

Thank you for this PR. It would be great to be able to use the Lidar on an F1Tenth car. The the code looks very good; I have left a few comments. There are other concerns:

• is there a parallel PR for the docs? Without documentation on how to setup the Lidar the software is not that useful and it becomes a maintenance burden. Links out to reliable, stable content can do most of the work. It would also be great to have a video of the webui output.
• we should also mention in the camera section of the docs about how to setup the 'camera' to be the lidar scan. That is a really good idea.
• we should rebase/squash these two commits into a single commit.

[Ezward]

This is very interesting. So the idea here is that the lidar plot would be used as the input to the CNN? Separate from the code concerns, have you tried this? Does it produce a reasonable autopilot?

[mgagvani]

I was thinking more along the lines of being able to see what the lidar sees. I haven't tried to train an autopilot with it although that does sound like an interesting idea.

[Ezward]

These values need to have defaults based on the chose lidar type. RP/YD would be 0 for angle and I'm not sure for distance.

[mgagvani]

Do you mean these should be set to zero for the user to put in themselves? I wanted to give this example to show that the back half of scans should likely be discarded in most set-ups. As for the max distance, I think this is reasonable for the entry level RP Lidar/ YD Lidar. If someone buys a fancier model then I would assume they would also know how to change this value to reflect the capabilities of their lidar.

[mgagvani]

Thanks @Ezward for the review, I'll probably get to the fixes/writing docs in a week or so.

[mgagvani]

Hi @Ezward I addresssed your review and made a PR for documentation: autorope/donkeydocs#56