WIP : user groups list
rename CampaignContainer -> DisplayCampaignContainer
Email campaign, part 1
move routes

That way, we can separate /campaigns/display and /campaigns/email
split the campaigns page in two

Now, the page displays display campaigns and email campaigns.
add a deletion button on the campaign list
new image for the email campaign
campaign buttons : show them on hover
email campaigns : show the link to the user groups
user group list/edition/deletion