add editorconfig and enhance/fix vagrant install/instructions

[rubo77]

• add .editorconfig with indentation settings for the whole project
• update default node list URL
• Add some more troubleshooting info in README and bootstrap.sh
• enable automatic update check for the vagrant box
• add apt upgrade

[RalfJung]

bors r+

[bors[bot]]

Build succeeded:

• continuous-integration/travis-ci/push