Merge pull request #2442 from Benglin/RC0.7.2_Revit2015

Increase reference count for array elements
Disable reporting of heartbeats to analytics

GAE limits sessions to 150 events. The use of a heartbeat is currently limiting the recorded session length to ~2 hours. Disabling for now.
Fix crash when invoking Form.ByLoftCrossSections with null input.