[WIP] Campaign creation

Apologies for the long PR. This allows admins to create and edit campaigns. What's been implemented

- Creating campaigns
- Viewing campaigns
- Editing campaigns

What still needs to be done:

- Deleting campaigns
- Fix image issue, images are not being uploaded by Carrierwave for some reason
- Callback in campaign model is not firing to deactivate other campaigns if current one is set as lead
- Style the lead campaign in the home page view