display merge options in UI
split import handling code into separate module
import and treat imported as truth
allow merging of contacts both ways
test to make sure we are not butchering groups
update_contact() already preserves existing groups
tests for leaving properties & subscriptions alone
only prefix extras if theres a collision in names
Merge branch 'develop' into feature/issue-919-allow-contact-updating-on-import
make sure to check the contacts value (thanks @justinvdm)
leaving stuff as is with a NOTE
Merge branch 'feature/issue-919-allow-contact-updating-on-import' into develop