release version 2.9.0

reverted a problematic fix

Merge branch 'develop' of github.com:secure-software-engineering/Flow…

…Droid into develop

Merge branch 'master' of github.com:secure-software-engineering/FlowD…

…roid into develop

Merge branch 'master' of github.com:secure-software-engineering/FlowD…

…roid into develop

fixed the dependencies of the 2.6 release version

Update README.MD