Started work on GUI.

The GUI is a DLL so I can reuse in other games. Very basic at the
moment, not really in a useable state.
Further work on GUI.

Added new GUI elements. Incorporated more into the H.U.D.
Created Gui System.

Made to make creating the GUI easier. Also adjusted the way the Controls
load their content.
Class Organisation.

Also fixed an error in the constuctors for GuiTextBox.cs.
Resource Organisation.
Start Menu implemented.

And many other adjustments which I was supposed to commit beforehand...
Start Menu Complete.

Now all to do is the Options Menu, and code the Exit button. Continue
will be done at a later date.
Added comments to StartMenu.cs
StartMenu added E as alternative to Enter.

Also changed it to use CurrentKeyboard Varible.
Renamed GUIFont.spritefont

Added "Made by Nathan Todd" text to Start Menu.
Created basic resouce management.

Improved Start Menu, and added Options Menu.
Options Menu on hold.

Options Menu will be on hold until a later date.
Merge pull request #2 from Spikky577/GUI-HUD

Gui hud