Add option for initiatives to inherit start and end dates from rolled up (child) initiatives Merged

Consider the following use case:

• user has large initiatives at the Product Line level (e.g. Enter Japanese Market; scheduled for Q1 & Q2), and then sub-initiatives at the individual Product level (translate interface to Japanese; scheduled for Q2). 
• Product level initiatives are rolled up to Product Line level initiatives
• user now wants to shift Product level initiative from Q2 to Q3

At the moment, the user has to change timings in two places: shift the Product level initiative to Q3, then extend the Product Line initiative to end in Q3.

When dealing with dozens of initiatives / sub-initiatives and complex roadmaps, this becomes unwieldy.

SOLUTION: Provide an option for initiatives to inherit the start / end dates of any rolled up initiatives. That way product line initiatives will resize their timings dynamically based on any shifted sub-initiatives.