Adding (deactivated by default) a button next to label fields to show a help pop-up.
This is useful when the current help text is too long. If you try to scroll down on the current help window, you will overmouse over other fields, changing the text on the help window.
Merge branch '2.10.x' of github.com:geonetwork/core-geonetwork into 2.10.x
Merge pull request #517 from Delawen/2.10.x

Help popup on editor (deactivated by default on css)