Allow counters to be removed. If an operation finds out that the counter doesn't exists, it is recreated with its initial value and the operation is replied.

If a getValue is invoked and the counter doesn't exist, it returns its initial value without recreating the counter.

New methods to the API:

CounterManager.removeCounter(String counterName) //remove the counter with this name 
StrongCounter.remove() //removes the counter represent by this instance
WeakCounter.remove() //same as above