API: Node start and end functions

Following are what I call startup and ending functions that are called during some kind of (un)initializing process. I have also described at what event they are called in Maya.

-initializePlugin()

-uninitializePlugin()

-Constructor

-Destructor

-MPxNode::initialize()

Sequence in which these functions are called:

MPxNode::initialize()
When a node plugin is loaded this is the first function to be called.

initializePlugin()
After above function is called during loading of the plugin.

Constructor
When a node is created, e.g. using createNode.

Destructor
When node is deleted and it is not referenced by undo queue (imp).

uninitializePlugin()
When a node plugin is unloaded from Maya.