Create only/NoRemove global config elements

[KevinJump]

Ability to make a handler only create new items (so things where the item doesn't already
exists).

<Add Key="CreateOnly" Value="true" />

Ability to make the handler not delete items or properties.

<Add Key="NoRemove" Value="true" />

also the ability to set these values globally, via a new HandlerDefaults section in the settings - so they can be set per handler or globally.

<HandlerDefaults>
	<Add Key="CreateOnly" Value="true" /> 
	<Add Key="NoRemove" Value="true" />
</HandlerDefaults>

[KevinJump]

ac6f5be & 5d8f62e