Backend overhaul

[GustavoSilvera]

This is a large PR that includes various (mostly-backend) fixes and improvements. Listed in order of importance:

1. Add support for multiple EgoVehicle types (ex. more than just the Tesla Model 3). Currently include also a Jeep, a Mustang, and a Vespa for example, as well as a tutorial on how to add your own.
2. Adding smart(ish) pointer management for all the major pointer connections between the major DReyeVR classes to help protect against eager garbage collection, object ownership, & dangling pointers (fixes a bug where replaying a recording that switches maps would crash the game bc dangling pointers to the original map were dereferenced; now this is more safely handled and pointers can be checked for validity before dereference).
3. Revamping the custom configuration/parameter file class to use a new ConfigFile class that is more flexible and lends itself better to splitting the parameters between general DReyeVR things and specific-vehicle params (like where the camera goes in each particular vehicle mesh). Also adds a recording/replay correctness warning by comparing the loaded config files with those that were used at the time of recording.
4. Adding steering wheel face buttons using DReyeVR custom actor API. These are lightweight (non-recorded) and helpful for user feedback visualization.
5. Adding logic for (physical) steering wheel to follow vehicle wheels (ex. during autopilot) and with a user-tunable threshold for manual takeover.
6. Fixed a bug where the custom shaders were not being cooked in package mode, resulting in only RGB camera mode.
7. Added minor PythonAPI fixes and a __init__.py startup script to ideally better load the DReyeVR files into the python path.

[ajdroid]

this is a great idea and why doesn't carla do it already

[GustavoSilvera]

Not sure, I only recently realized we could do this and it makes the PYTHONPATH stuff a lot easier.

[ajdroid]

I recommend naming the Docs/EgoVehicle.md file to be something like New/CustomEgo

[ajdroid]

Let's give a little preview:

See Docs/Tutorials/ to view several DReyeVR tutorials to view several DReyeVR tutorials such as customizing the EgoVehicle, using our CustomActor API and others.

[ajdroid]

@GustavoSilvera

[ajdroid]

Looks good to me -- excellent work here @GustavoSilvera !