Updating a property unsets unrelated property

[Nicolas Raoul]

Steps to reproduce:

1. Have an item with nemaki:groupId set to some string
2. Perform via OpenCMIS an updateProperty with a map containing only a nemaki:users key-value
3. The nemaki:users value has been correctly affected, but unfortunately nemaki:groupId is now unset

This is contrary to the CMIS protocol which says "properties not sent are retained".

[Nicolas Raoul]

https://github.com/aegif/NemakiWare/blob/integration/core/src/main/java/jp/aegif/nemaki/businesslogic/impl/ContentServiceImpl.java#L1180

[Nicolas Raoul]

properties contains a non-null nemaki:users value, but buildSecondaryTypes returns an empty list.

[Nicolas Raoul]

Fixed by #245