docs: Add GUI.md

Change-Id: Ic7ffb8dea4521af95cb87e578be3eb46af6e8f6e

docs/GUI.md

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+Mini-NDN Edit
+=============
+
+Mini-NDN Edit is a GUI program designed to simplify the creation of Mini-NDN topology
+configuration files. Mini-NDN Edit allows the user to build a topology, configure the hosts and
+links, and generate a topology file that can be used by Mini-NDN.
+
+![minindnedit](img/gui/minindnedit.png)
+
+## Working with topology files
+
+#### File formats
+
+There are two file formats used by Mini-NDN edit.
+
+* ``.mnndn`` files store topology information used by the GUI. Mini-NDN Edit can open and
+save ``.mnndn`` files.
+
+* ``.conf`` files are used by Mini-NDN to create and run topologies. Mini-NDN Edit can generate a
+``.conf`` file from a ``.mnndn`` file. Mini-NDN edit cannot open ``.conf`` files. Please see
+[CONFIG-FILE.md](CONFIG.md) for more information on the content and format of ``.conf`` files.
+
+#### File menu
+
+![file-dropdown](img/gui/file-dropdown.png)
+
+* **New** - Erase the current canvas and provide a new empty topology
+* **Open** - Open a ``.mnndn`` topology file
+* **Save** - Save the current topology as a ``.mnndn`` topology file
+* **Generate** - Convert the current topology to a ``.conf`` file runnable by Mini-NDN
+* **Run** - Run the current topology in Mini-NDN. The GUI will disappear and Mini-NDN will run on
+            the command-line.
+* **Quit** - Exit Mini-NDN edit
+
+## Tools
+
+### Cursor tool
+![cursor-tool](img/gui/cursor-tool.png)
+
+The *cursor tool* is used to select and move nodes in the topology. A selected node or link can be
+removed from the topology using the ``backspace`` key or by selecting ``edit/cut``.
+
+### Host tool
+![host-tool](img/gui/host-tool.png)
+
+The *host tool* is used to add a node to the topology. Click on the canvas to create a new node at
+the mouse cursor's position.
+
+### Link tool
+![link-tool](img/gui/link-tool.png)
+
+The *link tool* is used to connect two nodes with a network link. Click on a node and drag the mouse
+cursor to another node to create a link between the two nodes.
+
+## Configuration
+
+#### Editing host information
+
+To edit a host's information and configuration, right-click on the desired node and select
+``Host Options``.
+
+The *Host Options* window will include tabs to modify the node's properties as well as the
+configuration files for NFD and NLSR on that node.
+
+*Note: Network, Site, and Router in the NLSR tab are unused in v0.1.0*
+
+![host-config](img/gui/host-config.png)
+
+#### Editing link configuration
+
+To edit a link's configuration, right-click on the desired link and select ``Link Options``.
+
+The *Link Options* window will allow configuration of the link's bandwidth, delay, and loss rate.
+
+![link-details](img/gui/link-details.png)