Bulk subtask action: convert to issue and change parent

Provide the ability to convert more than one subtask to an issue as well as provide the ability to change the parent of more than one subtask.

This is helpful when a user determines that they have logged subtasks to the wrong parent (in our case, many of our parent issues have 25+ subtasks because we use them for tasking for each project milestone or general task like a release). Or, they have determined that the subtasks are too high level and need to have their own subtasks - thus, they need to convert to issues.