Added help box to skillEditor

The help message is shown until the user closes it.
Added another help box to skillEditor

Added a help box to the 'edit as a prerequirement' tab.
Added a 'show help' button to skillEditor
Improved HintModelView cookie code
Changed 'show help' button to be hidden on certain tabs (skillEditor)

The button is now hidden on 'Course information' and 'Comments' tabs
in skillEditor.
Fixed skillEditor help alert and button to work with competences
Merged skillEditor help message additions into master
Fixed one missing localized string in skillEditor