Already installed package cannot replace other packages

The current implementation of the installer is only able to replace components when the "replacement" package is not already installed. It should be possible to simply merge functionality of components and remove the deprecated one in favour of the one implementing the functionality of both.

Example:
V1 contains "Component A" and "Component B". In V2 the functionality of "Component B" has been merged into "Component A" and "Component B" gets removed.

Currently, adding "Component B" into the "Replaces" of "Component A" will do nothing because "Component A" is already installed during an update.