Default comparator for sorted collections. It uses the service id property of an OSGi service to determine the order.
Thus, by using this comparator, the services added to a collection will be sorted in the order in which they are
published to the OSGi platform.
This comparator version, provides
natural ordering for service references for pre OSGI 4.1 platforms,
using the contract from OSGi 4.1 spec:
If this ServiceReference and the specified ServiceReference have the same service id they are equal.
This ServiceReference is less than the specified ServiceReference if it has a lower service ranking and greater if it
has a higher service ranking. Otherwise, if this ServiceReference and the specified ServiceReference have the same
service ranking, this ServiceReference is less than the specified ServiceReference if it has a higher service id and
greater if it has a lower service id.