Tasks/constraints refactor + Reduced TSID formulation

[ibergonzani]

Same as #30

Refactor for tasks (previously called Constraints) and actual linear constraints.

• Rename Constraints to Tasks (ConstraintConfig -> TaskConfig, ConstraintStatus -> TaskStatus)
• Add specific classes for linear constraint
• Add TSID Scene (AccelerationReducedTSIDScene) that leaves torques out of the QP optimization and computes them afterward

Currently added linear constraint:

velocity:
joints limits (velocity, position)
contacts (xero vel)

acceleration(tsid):
joint limits (acceleration, velocity, position, effort)
contacts (zero acc)
rigidbody dynamics
effort limits (for TSID Reduced scene)

In addition to a vector of tasks, a scene has now a vector of vector of constraints
Inside the scene update, they are updated automatically using a RobotModelPtr (update implementation inside constraint class, not scene)

since the joint limits constraints need the control loop time dt. this is passed to the scene through the costructor (default parameter to avoid break existing code).

At the moment all constraints are hardcoded inside of Scenes
In future they might be passed through the configure method?

[dmronga]

Thanks for contributing. I will take a look once I am done with robot models

[ibergonzani]

Added TSID reduced (no torques in QP) scene

[ibergonzani]

Tests are working fine but scene benchmark fails often in the VelocitySceneQuadraticCost because of jointLimits.
At times, Joint position of actuated joints seems to be outside of bounds with the hyrodyn_hybrid model.
(in base branch the joints position is not enforced)