Update Manager
UpdateManager is the central component of the NERD daemon, controlling data flow between modules.
It processes update reuqests issued by modules (by calling UpdateManager.update() method), loads records from database, applies the requested changes, and calls handler functions registered to these changes.
TODO: More detailed description.
Basic functionality of the main processing function is outlined on the following diagram:
Note: This is a simplified version describing the basic operation. In reality, there are several details that make it more complicated. Diagram of the complete algorithm can be found here.
