Implementing refinements in the webui: dividing forms for selecting the context and uploading json files in the home page; listing and detailing existing services.

- Each device type has a particular icon
- Icon color represents real/emulated devices
- Nodes support drag/drop
- Nodes are auto-placed in the topology
- Nodes have a tooltip showing their name/id

- Added upload of descriptors file
- Added scripts to generate descriptor files
- Arranged minor script details
- Minor bug fixing