Analysis of external mesh loading libraries and comparison with the existing approach

Desired behavior

Be able to load glTF2 and FBX mesh files into Gazebo.

Alternatives considered

Only alternative is on the user side, which creates additional step for converting mesh files into Ignition Gazebo readable format.

Implementation suggestion

There are two ways to extend the capabilities of the Gazebo's mesh loading system; (A) Using an external open-source library or (B) Writing glTF2 and FBX mesh loaders in a consistent way with the current approach.

Analysis is required to decide which approach is better. I am planning to generate such analysis in the next couple of days, so any idea is welcome. Currently gathering ideas around the internet to make a suitable comparision.

I created an additional document for this analysis in here. I will start my analysis with assimp.

Additional context

1. Currently working on a creating a connection between the assimp library and Ignition Gazebo.
2. Possible related issues #173,