Implement a file format for axibot jobs about axibot

[storborg]

Some more detail on this:

• Add an axibot plan tool which outputs a saved job file.
• Allow axibot info or axibot plot to accept either a .svg or .axibot.json.
• Allow server uploads to be either a .svg or .axibot.json.

[storborg]

In the future it would be cool if .axibot.json could also contain configuration parameter overrides.

[storborg]

So actually, it doesn't really make sense for the configuration parameters to be included in the job, because the job already implicitly includes the speed, servo positions, etc.

Instead, it's necessary that the job include the servo setup parameters based on the configuration parameters that were used when the job was originally planned.

[storborg]

Those parameters are the pen up position, pen down position, and servo speed.

[storborg]

Started this in 4ffd9fc but the web interface still has some edge cases that need cleaning up.

[storborg]

Wrapped up in 7f19bc8 and d83d5a1