Also set back to java8 (Android is supposed to support it now
and it turns out our tests failed since they use a lambda...).

(Initial preparation for Android compatibility - incomplete due to rsb)

Manually integrated the following changes from b8466a (master 2015-11-13)

- Blackboard classes by hvanwelbergen
- Blackboard test by hvanwelbergen
- Payload merge fix by hvanwelbergen
- rsb Buffer fix (by myself) copied but inactive (not needed atm?)

Please refer to the logs of the legacy-str branch for a full history
of the respective changes.