`Movable`: new member variables for speed and acceleration etc.
`Movable`: new member variables for speed and acceleration etc.

These new member variables are to be used from the `Brain` callbacks
etc.

`yli::ontology::Waypoint`, which inherits `yli::ontology::Entity`,
needs to be implemented.

`Waypoint`-`Movable` is some kind of master-apprentice relationship and
needs to be implemented as well.

nrz/ylikuutio,nrz/ylikuutio,nrz/ylikuutio,nrz/ylikuutio