refactor configuration

Split accounts and paths for DRY pattern. Allow to specify server url to work with any webdav servers other than nextcloud.

account:
  # full url so we can adapt to any usecase
  url: https://drive.itsufficient.me
  # optional for DRY when using relative paths
  path_prefix: /remote.php/dav/files/backup
  # credentials
  user: backup
  password: xxx
paths:
  # path alias to use as shortcut for cp, rm, ls, clean
  gitlab:
    # path is relative to path_prefix if it doesn't start with /
    path: itsufficient.me/db/gitlab