Improve administration panel

[x] edit a member
[x] delete a member via a bootstrap modal appearing by clicking a 'delete' button
[x] member: filter by position (admin/user/banned)
[ ] member: order by alphabetical (ASC/DESC)
[ ] member: order by birthday (age?) (ASC/DESC)
[ ] send email to member when banned
[x] edit an event
[ ] delete an event via a bootstrap modal appearing by clicking a 'delete' button
[ ] event: order by date (ASC/DESC)
[ ] event: order by capacity (ASC/DESC)

stephane-rbn / soundbase