Provide a feature to select an active Sprint from a board

Problem Description

When a board contains multiple parallel active Sprints, Portfolio only imports one active Sprint per board and there is no way or option to select which Sprint to be imported. It also does not allow sprints to overlap in any way, even if the start date of one sprint takes place before the end date of another.

Suggested Resolution

Provide an option to select which active Sprint to be imported from a board, and allow Portfolio to recognize and take advantage of the parallel sprints functionality, as right now it does not seem to know how to handle them properly.