Including obstacles in the mobility model

[aarizaq]

I don't know if this is in the future plans, but I think that could be a good idea to include the obstacles in the mobility models This is an example for the RW model, but the changes can be set in the MobilityBase and the only change that will be need to do in the models is in the method setTargetPosition

https://github.com/aarizaq/inetmanet-4.x/commit/2d6977d65967fbd2d58adb2cc584edce4c7de551