Company users

Story http://jira.jessetilro.nl:8081/browse/BEP-362

• Admin: add all clients to project show
• Admin: add panel on which admin can add/remove role of company users
• Admin: add all employees + registrar to company show page
• FEI: add 'become contact person' button on project page for employees
• Add mailer to invite new employees to company
• Add tests.
• Add notifications.
• Add button to accept employee invitation
• Limit functionality of company when not member of the company.

To Do In the Future:

• Setup mail configuration.
• Add button to leave company?

Jenkins failure is due to brakeman failures in the development branch.