Change Workspace.summary to have samples as rows (not groups)

[whitews]

The group concept in a FlowJo workspace is somewhat odd. Each sample can have only one gate tree and it is tied to the sample regardless of which groups the sample belongs. This means that 2 samples in the same group may not have the exact same gate tree.

The current Workspace.summary() method was lifted from the old Session.summary(). In the old Session class a sample could belong to multiple groups and have a different gate tree in each, but all samples in the group had the same gate tree.

Change the Workspace.summary() method to return a DataFrame based on samples and not groups.

[whitews]

placing on hold for now as I'm unsure what the best approach is