Added grid2grid example

[andreaantonello]

This example shows how to set-up a grid to grid tool-path for pick and place use-cases. This allows to use the API to loop between two completely parametric grids: the number of columns, rows, their respective pitch, the relative orientation, the objects' pickup angles and the grid's elevation are fully definable by the user.

[Charlesworth]

Overall this is great, good work on the example, especially the interactive plot! Needs some cleaning up (I've added comments) and overall:

• Avoid global state, in particular you are defining and using config all over the place
• For naming, avoid using underscore prefix for non private variables or non descriptive names, i'd recommend taking a que from the python PIP defined naming policies for advice
• Try and separate code by concern, i.e. the plot stiff should probably be separate from IK helper functions, evaGrid seperate from main

I think this will probably take a couple of review iterations so bug me to re-review quickly!
Cheers

[andreaantonello]

Removed global variables, grouped EvaGrid related instances, removed dates and unused functions, cleaned up code in general.

[Charlesworth]

We have a question to answer before approving this PR, what level of support and quality do these examples require?

So far the code is acceptable and works but lacking in some respects (readability, best practices, style choices, separation of concerns), but as a research example I think this is great.

If we're expected to support this code for customers we should really sit down and refactor this together as the review is going to take a many iterations. If we're happy that this is unsupported example code I think this is fine, it works and proves a use case nicely (plus we state on the python_examples README that it's all unsupported). Let's have a quick chat about this tomorrow, possibly pull Mathew in as well.