Minimize setup steps

[fviernau]

Ideally the user would just need to copy and paste a single install command into the terminal and after it's execution, which doesn't require user input, is ready to run - with zero configuration.

Parts of this could e.g. be accomplished by introducing a configuration directory like ~/.orthw-home and placing
the needed repository clones under that dir, like e.g.:

~/.orthw-home/repos/ort
~/.orthw-home/repos/orthw
~/.orthw-home/repos/scancode-toolkit
~/.orthw-home/repos/ort-config

and for the config this could be extended to:

~/.orthw-home/config/orthw
~/.orthw-home/config/ort

Maybe also mounting custom configuration files into docker could be simplified / implemented by just a directory:

~/.orthw-home/config/docker-home

All the above could be initialized with reasonable default so that the user does not need to configure anything.
If the user then wants to use a custom let's say ort repository location, the respective directory would just need to be replaced by a symlink.