WIP: Enable operations that write to the DB to be rolled back on error by wrapping them in transactions.
WIP: Enable operations that write to the DB to be rolled back on error
by wrapping them in transactions.

Refactor: Flatten structure of AVMManager.removeFeature method for
better readability.

itsjeyd/ODE,itsjeyd/ODE,itsjeyd/ODE,itsjeyd/ODE