update version to 1.6.0; prepare and write instructions how to make next
version change with one command `mvn -Dtycho.mode=maven
org.eclipse.tycho:tycho-versions-plugin:set-version
-DnewVersion=1.7.0-SNAPSHOT`
Merge pull request #39 from Enide/master

update version to 1.6.0; prepare and write instructions how to make next