Clarify address specification

Thom Wiggers
2018-11-05T11:54:03+01:00

Closes #746

#### Previous behaviour
Steps to reproduce:

1. Enter `1 kerkstraat`
2. Get a confusing message

#### New behaviour
Steps to validate that it works:

1. Enter `1 kerkstraat`
2. Get a message telling you to put it after.