Add New Mapping Interface and Environmental Model

[bpwilcox]

Support an extensible framework of map representations via a Mapping Interface and incorporate relevant static, dynamic, object, and semantic map data into an Environmental Model to be used by map dependent algorithms.

First aim is to support & refactor grid-based map representations such as grid_map, occupancy grids, and costmap_2d with further aim to support interface for other tree/node-based representations such as octomap.

[mbuijs]

An environmental model similar to this? https://github.com/tue-robotics/ed

[bpwilcox]

An environmental model similar to this? https://github.com/tue-robotics/ed

I did take a look at that repo. I think there are some interesting ideas to build from, though for the time being, we're going to focus on grid-based representations before we incorporate some of the more abstract object-based representations. An initial milestone for now would be to seamlessly integrate grid_map, occupancy grid, costmap_2d, and perhaps octomap into an environmental model which can support these types and provide useful contextual/semantic information about the current environment. We're currently using the "layer" concept, similar in ways to costmap_2d. This would then be the provider for localization, planning, and control.

[mkhansenbot]

I think this can be closed now as the environmental model (aka World Model) is being covered by #565