Add extra functionality

You can now install either the stable release or the development release
with the 3rd party script gitflow-installer.sh
Use a builtin function for removing exclamation mark.
Version bump 1.4.0-rc.1
Update of the contributers.
Version bump 1.4.0
Merge branch 'release/1.4.0'
Merge tag '1.4.0' into develop

Release of 1.4.0
Preparation for new development cycle after release 1.4.0