create at least one example that sources a resource (e.g. urdf file) from drake

[RussTedrake]

now that we've seen issues with finding resources (with FindResource) from external repos, I think it's important that we capture that in our example here. @siyuanfeng-tri was the one who battled through it most recently.

[stonier]

+1

[stonier]

@siyuanfeng-tri would the double pendulum demo be an appropriate candidate to make an example of here?

[siyuanfeng-tri]

@stonier yeah sure. Any model would fine. Last time I tried this, I was having trouble loading a abs path urdf into an RBT. FindResource complains that the file is not within drake basically.

[jwnimmer-tri]

Yes, never pass an absolute path to FindResource -- on the tin, it says to use relative paths.

[jwnimmer-tri]

(If you have an absolute path, then you can just call AddModelInstanceFromUrdfFile (or similar) directly.)

[stonier]

Resolved by #52