GPS signals simulator

[AvrahamOhana]

create a module that simulate the signals of GPS system.

some references found in google:
https://github.com/MartijnBraam/gpsd-py3/tree/master
https://gitlab.com/nmeasim/nmeasim

it's open to discuss about the features and requirements before we start to implement this feature.

for example:
include noise in the signal ?
simulate 'signal lost' situations ?

[C4dynamics]

we currently have navigation capabilities based on inertial line of sight, namely IMU and seeker.
we should also have the option of making inertial navigation based on GPS.
as first step we need to make a version of the example/six6dof based on GPS.