Add popup error handler abstract class, use that by default for errors we want to display, fix the non handled errors in stage stuff.

Conflicts:
	TaskManager/src/main/java/edu/wpi/cs/wpisuitetng/modules/taskmanager/views/NewStageView.java
comments, license headers
Merge pull request #39 from JustDuckItAll/fix-unhandled-errors

Add popup error handler abstract class, use that by default for errors w...
Merge remote-tracking branch 'origin/team3Master' into fix-comments-add-tests-yay

Conflicts:
	TaskManager/src/main/java/edu/wpi/cs/wpisuitetng/modules/taskmanager/apiclient/APIResponseHandler.java
	TaskManager/src/main/java/edu/wpi/cs/wpisuitetng/modules/taskmanager/views/NewStageView.java
	TaskManager/src/main/java/edu/wpi/cs/wpisuitetng/modules/taskmanager/views/TaskInfoView.java