Fixes and Improvements for web view of a lightning node

[Wolf-Raider]

this pull request contain the following fixes:

• Docker build fix. (python 3.7 is needed to build correct)
• fixed link to view the highest bitcoin block at the blockchain. (smartbit is down)
• fixed the fee calculation on the event list. (millisat fees where always round down)
• fixed the map view. (it is an memory overflow in your local browser, which kills the application. i filtered the view to only the nodes connected with your node with channels between them and you. this is i think also a nice view, how your node is connected. :) )

[Wolf-Raider]

this version is running at http://marburg.ddns.net