[graylog2-server] prepare release 7.0.2

[graylog2-server] prepare release 6.3.7

[graylog2-server] prepare release 6.2.10

[graylog2-server] prepare release 7.1.0-alpha.1

[maven-scm] copy for tag 7.0.1

[maven-scm] copy for tag 6.3.6

[maven-scm] copy for tag 6.2.9

[maven-scm] copy for tag 7.0.0

[maven-scm] copy for tag 7.0.0-rc.2

[maven-scm] copy for tag 7.0.0-rc.1