Implementations inside Log Class for Phase 1

Modifications needed to Log Class to complete the Phase 1 of the
project. Bascially implemented the body of the functions:

public synchronized boolean add(Operation op)
public synchronized List<Operation> listNewer(TimestampVector sum)
public boolean equals(Object obj)

The purgeLog() function was left empty because it's part of the last
part of the project. Next step for me now will be the TimeStampVector
Class, to complete this phase.