It avoids unnecessary inclusion and definition

Minor improvement to eiquadprog solvers: check problem size, remove useless variables, add comments.

Add two new versions of eiquadprog. EiquadprogFast is a slightly optimized version of the original solver that preallocate all the dynamic memory. EiquadprogRT (i.e. real time) is a version of the solver that uses static-size matrices. Both new versions have also much more documentation and provide more information to the interested user, such as number of iterations, number of active inequalities, maximum number of iterations and proper status flag in case the problem could not be solved.

[solver-HQP-eiquadprog] Make Hessian regularization more explicit in the code. Add commented draft code to handle equality constraints outside solver.

Preliminary version of the library (not working yet). In this version I just implemented the constraints, the constant trajectories, the robot wrapper and the task SE3 equality.