Implement full Lie Group Structure into `rust-inekf`

[lucaslibshutz]

This should include the group structure of $SE_2(3)$, along with all relevant quantities needed.

[lucaslibshutz]

Relevant current commit: cornellev/rust-inekf@64e43e5

I worked on implementing the state in $SE_2(3)$, along with the relevant math to go along with it. That will all be documented as shown in #113. Going to try and finish the unit test suite probably Wednesday as I want to work on some research stuff, with the goal to have the propagation model in by the weekend, along with understanding what measurement models I want to implement.

[lucaslibshutz]

This is pretty much done, except for a few things. Marking this as closed.