feat(logging): reduce log verbosity

[missinglink]

simple, partial fix for the issue mentioned in #278
this PR simply changes the logger to write only the error message and not the whole stack.

the log files contain many entries such as the one below, the stack itself isn't useful and the corresponding line number can be found easily with git grep 'invalid csv row' as its the only occurrence in the repo.

I expect that this minor change will significantly reduce the log size, at least for addresses with an empty NUMBER or STREET field.

invalid csv row Error: invalid street
    at Address.setStreet (/code/interpolation/lib/Address.js:71:11)
    at DestroyableTransform._transform (/code/interpolation/stream/oa/convert.js:37:15)
    at DestroyableTransform.Transform._read (/code/interpolation/node_modules/readable-stream/lib/_stream_transform.js:184:10)
    at DestroyableTransform.Transform._write (/code/interpolation/node_modules/readable-stream/lib/_stream_transform.js:172:83)
    at doWrite (/code/interpolation/node_modules/readable-stream/lib/_stream_writable.js:428:64)
    at writeOrBuffer (/code/interpolation/node_modules/readable-stream/lib/_stream_writable.js:417:5)
    at DestroyableTransform.Writable.write (/code/interpolation/node_modules/readable-stream/lib/_stream_writable.js:334:11)
    at Parser.ondata (_stream_readable.js:718:22)
    at Parser.emit (events.js:314:20)
    at addChunk (_stream_readable.js:297:12)
{
  LON: '22.9419749',
  LAT: '40.5794481',
  NUMBER: '1',
  STREET: '',
  UNIT: '',
  CITY: '',
  DISTRICT: '',
  REGION: '',
  POSTCODE: '',
  ID: '',
  HASH: 'gr/b/municipality_of_kalamaria:a31ca0d87194db14'
}

there's still way more we can do to mitigate #278, I suspect that developers rarely even read these logs, so maybe configuring the verbosity and only enabling high verbosity during local development would be preferable.