Merge pull request #4106 from aspangaro/develop-skype

htdocs/adherents/card.php

htdocs/adherents/card_subscriptions.php

htdocs/contact/card.php

htdocs/core/class/commonobject.class.php

htdocs/core/lib/functions.lib.php

htdocs/core/modules/modSkype.class.php

htdocs/langs/en_US/admin.lang

htdocs/theme/common/skype_callbutton.png

htdocs/theme/common/skype_chatbutton.png

htdocs/user/card.php