Create launchfile with world, bluerov, and mavros/ardusub

[Rezenders]

Bluerov model:

• https://github.com/Rezenders/bluerov2_ignition
• https://github.com/clydemcqueen/bluerov2_ignition

World model remaro_world

Mavors repo

Specify:

• robot start position (as a parameter)

[Rezenders]

I guess this is done, we are still missing to add ardusub but I am not sure if this will be necessary.