Update query project when switching datasources

[DHedgecock]

What does this PR do?

Adds checks that the configured query projectName matches the current datasource instance projectName configuration. This resolves two current issues:

1. Switching between instances of the plugin when editing a query currently fails to update the query's project name to match.
2. Using a template variable for the query datasource currently fails to update the query's project name to match.

Closes #33

How does this impact users?

Enables users to install multiple copies of the plugin with different projects configured for each copy. These copies of the plugin can then be used in a dashboard template variable, or to simplify switching between projects in the editor query mode by treating them as different datasources.

What needed to change in the code and why?

Checks on the query projectName were added to the query editor and the datasource request handler because the datasource project name can change without the query itself changing.

How did you test this?

Locally tested using a template variable setup.

Code review notes

none