Determine how .smapply dispatches functions

Usage

which_analysis(object, choice)

A list:

1.: A list of Regions (or combined, "dummy" Regions), for xapply operate on
2.: an ID for the analysis
3.: The cells for the analysis
4.: Logical indicating whether to override show.progress.

There are currently 3 possibilities that correspond exactly to those found in the which_returns function:

1. Region-wise analyses. In this case, the result of the iterator is simply returned to the SpatialMap
2. Formal Analysis objects. In this case, the Analysis is updated, and a splitting operation is performed to update each of the individual Regions that comprise the Analysis
3. Informal grouped Regions (e.g., grouping Regions by batch for normalization). In this case, no Analysis is added or updated in the SpatialMap, but individual Regions are updated.