Limit the amount of additional stations a user can add

[jkmnch]

Current behaviour:

Currently, we don't have a limit on the number of additional stations which a user can add. This means users can add as many fields as they like. This doesn't cause any issues with the service, but it's unlikely that users will need more than 10 additional station fields.

Feature request:

Add a max limit of 10 stations. Hide the 'Add additional stations' button when 10 stations have been added to stop users from adding more.