Performance tests

To get good numbers, close all programs before running, build & run outside of IDE:

cd /tmp
go build github.com/objectbox/objectbox-go/test/performance/
./performance

You can specify some parameters, see ./performance -h:

Usage of ./performance:
  -count int
    	number of objects (default 1000000)
  -db string
    	database directory (default "db")
  -runs int
    	number of times the tests should be executed (default 30)