Mechanism2d Java lacks SendableRegistry add and close

[shueja]

Mechanism2d needs to have SendableRegistry.add(this, "Mechanism2d", m_instance) and similar removal in close(). Currently, SmartDashboard.putData(mechanism2d) doesn't work because the registry doesn't have a name for the Mechanism2d.

[PeterJohnson]

I'm not sure we want this behavior, as unnamed Mechanism2d's don't seem very useful? You can putData() with a name, correct?

[shueja]

You can, but it's an API consistency issue. When only using one Mechanism2d and just trying to get it showing, I was thrown off by the fact that the "log-any-Sendable" putData didn't do anything.