Updated SM, SMP, ESW, and AIW

SceneManager -
Now contains a start scene and end scene.  These scenes are not
removable from the system and their names are not allowed to be edited.
After each addition/removal/edit, the SceneManager now checks to see
what scenes are reachable from the start scene and updates the graph
accordingly.

SceneManagerPanel - If the user attempts to remove a start or end scene,
the user is informed that they cannot do that.

EditSceneWindow
-If the user edits the start or the end scene, the title window disables
editing.
-When the user chooses to save a scene, the title is now crosschecked
with the database before saving it to the scene.   (Before the name
would be saved within the scene, then cross-referenced with the
database).
-The Add Item button now opens a fully functional AddItemWindow.  The
X's next to each item will remove the item that has been added to the
window (if an item is connected to the slot).

AddItemWindow
- Allows the user to select and item and choose whether they want the
item to drop on the scene or unlock the scene based on a drop down menu
choice.
- An item may only be dropped on one Scene, if the user tries to add the
item to multiple scenes, they are informed with a meaningful error
message.
- An item may not be dropped on the scene that it unlocks.  If the user
attempts to do this, they are informed with a meaningful error message.

Except for minor aesthetic and design choices, SceneManager,
EditSceneWindow, Scene, AddItemWindow, and AddConnectionWindow should
all be ready for implementation.  Any changes within the editor at this
point should not affect the running of the game.

-Tyrone
Bug and aesthetic fixes

EditSceneWindow
- Unlock items were being displayed in the dropped item area and vice
versa.  Reversed the fields.

- Changed the name of "Cancel" on EditSceneWindow to "Discard", now only
visible when adding a new Scene.

EditItemWindow
- Made it so the name of the item is the selected text when opening the
window

AddItemWindow
- Switched how the messages were being displayed in the drop down box to
match how they are displayed in the EditSceneWindow.

Tyrone
Added saving and loading for edit mode

MainWindow - Added functionality to save and load when selected from
file.

GameSystem - Added a saveSceneManager and a loadSceneManager function.

SceneManager
- Added a saveToFile that takes in a String of the file directory
followed directly by the file name and attempts to save the current
SceneManager details (Scene Graph and Item List) in XML format to file.
- Added a loadFromFile that takes in a String containing the file
directory followed immediately by the file name and attempts to load the
Scene Graph and Item List from the file given.

SceneTableModel
- Added a function that lets the caller set a new Scene Graph in the
SceneTableModel (used for loading from file)

ItemTableModel
- Added a function that lets the caller set a new Item List in the
ItemTableModel (used for loading from file)
- Added a column that tells the name of the scene where the item drops

Connected the XStream libraries for file I/O
- Tyrone
Mouse Over Descriptions

SceneManagerPanel and ItemManagerPanel now offer mouse over descriptions
of their data fields.

-Tyrone
Merge branch 'master' of https://github.com/jcote008/assignment3

Conflicts:
	src/Windows/EditItemWindow.java