MVP: Wrap Query Function - allow nested access

[dougbrn]

Feature request
Blocks #9. Implement NestedFrame.query to allow hierarchical column access, e.g.

NestedFrame.query("my_nested.a > 2")

The current thinking is that this returns back the full NestedFrame base layer, but would update the nested dataframe "my_nested" with the result of the query "a>2".

This can be accomplished by wrapping query and doing some string evaluation first to determine which layer to send the query to. I think to start we should limit a query string to only target one layer.

Before submitting
Please check the following:

• I have described the purpose of the suggested change, specifying what I need the enhancement to accomplish, i.e. what problem it solves.
• I have included any relevant links, screenshots, environment information, and data relevant to implementing the requested feature, as well as pseudocode for how I want to access the new functionality.
• If I have ideas for how the new feature could be implemented, I have provided explanations and/or pseudocode and/or task lists for the steps.