Follow-up fix for automatic calculation of area

[amplifi]

Cumulative project areas are re-calculated at each page load. To mitigate performance and scalability issues that may result in the project dashboard page being unusable for large projects and/or for partners on slower connections, the current implementation must be modified to store each project's cumulative area in the database, and maintain this value via trigger.

Targeted for completion in Sprint 20.

See #1534 for detail.