Set parameters

[JakubHazik]

Is possible set parameters for example sigma distribution of lidar beams or resolution of a map?
I talk about mrpt_icp_slam_2d package

[Logrus]

I will improve parametrization of all nodes.

[jlblancoc]

Great!
@Logrus : Just in case, take a look at the regression I inadvertidly introduced a few days ago trying to avoid pointers, here:
mrpt-ros-pkg/mrpt_navigation@76db0c7#diff-eafe347e79a69eca21d60da0a53ce9e7L79

It was fixed here: mrpt-ros-pkg/mrpt_navigation@75b539d

I can't remember if more nodes use the same approach of inheriting the Parameters struct (Node ==> Library), but it would be better split into two structs, as in my second commit above.