- PAStartMenu design changed
Added group layout to the frame.
Panel size fixed when resizable (top and bottom panel)
Changed LinkedHashSet to LinkedList

Reason to change is because LinkedList easier to modify positioning
within the collection
Added few functions to PASVGContainer: adding shape/shapes to group and
removing shape/shapes from group
PAGroup & PASVGContainer

PAGroup : create  new group; generate group id; check group existence
PASVGContainer : new constructor; 3x remove from group(tested for basics
only)
Merge branch 'develope' of https://github.com/kokhong20/SEPT-Assg