changed system that decides if upsync is allowed or not.

This can now be configured in kinds.js which is kind of a
config file already. So basically we can now enable
upsync in kinds.js without changes in syncassistant.js,
i.e. the code.

Signed-off-by: Achim Königs <garfonso@tratschtante.de>
Merge pull request #12 from Garfonso/master

changed system that decides if upsync is allowed or not.