[C2] Issues related to skills

[ywarnier]

• In the social network (home of the student), skills are not shown correctly (see screenshot below). Each skill should show a badge, and the badge should be clickable (point to main/skills/issued_all.php?skill=4&user=17 with the corresponding ids).
• In the social network, the link to see the skills wheel is still pointing to the old URL (skills_wheel.php). It should point to the new one (skills/wheel)
• In the social network, the link next to "Skills wheel", called "Skills ranking" points to main/social/skills_ranking.php but the resulting page is blank (you can see a table appearing briefly but it ends up blanked out). The same issue happens for the admin when accessing the skills ranking from the administration page.
• On main/admin/user_information.php?user_id=17 (clicking on student name from the admin's user list), the section "Achieved skills" should show the badges (or the default badge)
• On main/my_space/myStudents.php?student=17 (clicking on the reporting icon from the admin's user list), the section "Achieved skills" should show the badges (or the default badge)
• On main/skills/issued_all.php?skill=4&user=17 (clicking on any badge from one of the previous pages), badges should show
• On main/skills/issued_all.php?skill=4&user=17, the "Download badges" button should really say "Download badge" (without trailing "s") and it should only download one badge, the image (PNG) and not a list of badges (currently downloads an HTML page!?)

[christianbeeznest]

They are checked and improved with this commit e2e019c

Thanks for confirmation.

[ywarnier]

I added a few style changes, but all good. Thanks.