Prepare the interactive Web GUI

[EmreY]

Improve the basis Web GUI by adding interactive functionalities.

New functionalities:

• Load and execute a topology by selecting from the previously saved topologies list.
• Close a currently active topology.
• Show the selected topology as a figure.
• Show the details of the VMs (CPU, RAM etc.).
• Show the usage statistics (CPU, RAM etc.) of VMs for the active topology.

This issue requires the API on the backend to be implemented.