Tray Seeding Report: Only Field Areas in While Editing

[FutzMonitor]

Current Functionality

When editing a row in the Transplanting Report, the dropdown for areas currently displays all available areas. This is undesirable as transplanting logs, the movement of a tray seeding from a greenhouse area to a field area, should not have their area changed back to a greenhouse by users.

Desired Functionality

It would be best if the users weren't given the option to change the area of a transplanting log back to a greenhouse area. This means that the JSON objects for the areas needs to be fetched and filtered to save only the field areas into an array that could be passed into the computed method that makes the editing data available to the user while in editing mood. There is no need to worry about seeding types because this report only contains transplanting logs.

[FutzMonitor]

I can take a look at this issue since it's very similar to #585.