New grains added

[MateusStano]

Short Description:
Add different grain geometries to the motor class

Long Description:
Several methods of the Motor class make calculations based on grains with cylindrical geometries, implement the necessary changes in this class to be able to simulate grains with different geometries, example: star grain

Useful links:
https://www.nakka-rocketry.net/; https://github.com/reilleya/openMotor