Some easy to replace "q" calls have been replaced by "DBA" calls (#5632)

Some easy to replace "q" calls have been replaced by "DBA" calls (#5632)

* Some easy to replace "q" calls have been replaced by "DBA" calls

* Simplified the GUID creation

* And one in the API ...

* And OStatus has got some DBA calls more

* Just some more replaced database calls

* The event query is now simplified

* Events are now shown again

* subthread is now using the DBA calls as well

* Some more replaced database calls

* And some more replaced database calls and prevented notices

* Better use gravity

* Some more replaced database stuff

* Some more replaced database calls in DFRN.php

* The gcontact class now has got the new DBA functions as well

* The Contact class is now changed to new database functions as well

* Small correction

* We can now delete without cascade

* One more functionality is safe for future changes