Print robot context definitions in order

[xsebek]

From #7:

It may be necessary to add something to keep track of the order of the definitions (something the robotEnv does not care about) so that we can pretty-print them to a file in the same order the user entered them.

Add a panel showing the robot context of the focused robot to UI.

Ideally, use it in the robot Web API endpoint so we can inspect the robot context at runtime.

[byorgey]

I think some of my previous comments were confused about this, but note that an Env is not the right thing to use to recover the definitions of terms. An Env tracks runtime values of variables. Contributing to the confusion is the fact that in the case of variables denoting functions defined via def, we can sometimes do an OK job extracting a definition from its runtime value, because its value is simply a delayed expression. However, even in that case its value has been elaborated to contain things like force and so on. What we really need is simply an ordered map from names to definitions.