Merge branch '21-an-organization-does-not-appears-in-the-selectable-one-for-a-campaign' into 'master'

Resolve "An organization does not appears in the selectable one for a campaign`"

Closes #21

See merge request !11

Merge branch '21-an-organization-does-not-appears-in-the-selectable-one-for-a-campaign' into 'master'

Resolve "An organization does not appears in the selectable one for a campaign`"

Closes #21

See merge request !10

Resolve "Conceptions des interfaces"

Closes #12

See merge request !9

Resolve "Improve the usability of admin interface and models"

Closes #18

See merge request !7

Resolve "Add a way to use markdown formatting for some fields."

Closes #17

See merge request !6

Resolve "Fix the path for organization logo"

Closes #16

See merge request !5