Simplify yumi_hw launchfiles

[YoshuaNava]

The current launchfiles are too many (4 for launching YuMi on gazebo, 4 for working on a physical one), only a couple lines of code change between them, and they don't provide any information as to which control interface will be used (EGM or RWS).

As a first step, we could divide the launchfiles in:

• yumi_egm_vel_control
• yumi_rws_pos_control
• yumi_gazebo_vel_control
• yumi_gazebo_pos_control

And have groups in the launchfiles to select which controllers we will use, by means of a "use_traj_controllers" parameter, as recommended by @diogoalmeida.

The changes related to this enhancement would be introduced at a slow pace, keeping the current launchfiles until the others are well tested and documented in the wiki.

[diogoalmeida]

Is this related to the fact that you could select which control mode you want through a launch file argument, instead of having several launch files where only a couple lines change?