[maven-release-plugin] prepare release 1.6.0
[maven-release-plugin] prepare for next development iteration
Merge remote-tracking branch 'origin/1.6.0-SNAPSHOT' into 1.6.1-SNAPSHOT
Merge branch '1.6.1-SNAPSHOT'

Conflicts:
	assemble/pom.xml
	core/pom.xml
	docs/pom.xml
	examples/simple/pom.xml
	fate/pom.xml
	maven-plugin/pom.xml
	minicluster/pom.xml
	pom.xml
	proxy/pom.xml
	server/base/pom.xml
	server/gc/pom.xml
	server/master/pom.xml
	server/monitor/pom.xml
	server/native/pom.xml
	server/tracer/pom.xml
	server/tserver/pom.xml
	start/pom.xml
	test/pom.xml
	trace/pom.xml