Lots of fixes to numerous quirks, for example:
- PUT can now update productType
- GET returns productType
- GET and POST serialize scandinavian characters correctly
- Product's minAge and maxAge are now minimumAge and maximumAge
- Productype db queries now use slug (THIS MEANS THAT API SHOULD USE PRODUCTTYPE'S SLUG!!!
- Better error handling for missing producttype field

Also, do a migration. Note also that the minimumAge and maximumAge will be null after migration SO BE WARY WHEN PULLING THIS TO THE SERVER!!!!!!!!!!!!!
/api/producttypes now returns list of slugs, not names
Merge branch 'devel' of https://github.com/koulutuksenpilvivayla/pilvivayla-basaari into devel