Heads up! Version change for Ozone 2.0.0

[Wei-Chiu Chuang]

Finally got the time to do this,

I'll be renaming the release version "1.5.0" to "2.0.0". Will also add a
future release version 2.1.0 and star to move out jiras to 2.1.0.

And then update the version string in the pom.xml from 1.5.0-SNAPSHOT to
2.0.0-SNAPSHOT.