Change maps_package by map_path

[RomanRobotnik]

What do we want to achieve?

Change the current way to set the location where the maps are save.
Currently it requires a package, since it was intended to save maps inside the specific packages.
Now we want to set the full path, independent from any ROS package.

How do we plan to do it?

Change the function to get the file based on a package path. Instead of that it will use the full path provided by param.

How can it be tested?

Change the param from package name to path and see it runs correctly