Provide a portable app for Testnet

[2-towns]

Provide an app (Electron) that could be use for Testnet including features:

• Upload a file
• Download a file
• List the files uploaded
• Change the log level

Will try to do these things:

• Improve the debug info display
• Provide a component for storage request

FYI @veaceslavdoina

[2-towns]

There are small tasks to finish to deploy the app for Testnet :

• [X] Clean and reorganize the layout
• [x] Fix a style bug for the input group
• [x] Check the responsive
• [x] Add content for the help page
• [x] Add a ALPHA version beside the logo to make sure that people understand if is an early version
• [x] Add an empty placeholder when there is not favorites
• [x] Retrieve the file metadata from the uploaded file
• [X] Handle the errors and use Sentry to report

@veaceslavdoina I may try to reuse the Table and Modal component to implement quickly a way to create availability for hosts.