[Fellowship Nominations] Rework the fellowship nomination system and UI

Create facilities for the nomination of new fellows according to the by-laws §1.3.4.

• Creation of new Nominations
• Specification of specialties
• Starting voting rounds
• Pre-select default outcome for each decision
• Email invitation option after election
• Create Fellowship object and log events on successful acceptance
• Check that permissions are respected during data modification and display
• Check that fellows with conflict of interest are not added to the voters list