Add an option to specify separator string

This is especially useful in bidi apps, but also when you want to
specify a separator string different from the default "comma-space"
Add Arabic i18n files

Plus corrections to the French main extension file
Identify correctly the files
Merge remote-tracking branch 'remotes/tellibus/master'

Conflicts:
	i18n/jquery.multiselect.fr.js
	src/jquery.multiselect.js
	src/jquery.multiselect.min.js