Added Javadoc comments

Specifying that passing null pointers to constructor is illegal.
Added test cases for Review object
Minor cosmetic changes
Added toString() implementation
Fixed equals method
Added Javadoc comments and toString()
Moved in ratings parameter

From Entry class to Review class
Minor changes

removed unnecessary manual toString() calls
Added Javadoc comments
Implemented with Builder pattern

Unified with GameInfo class, provided builder pattern. Also added
Javadoc.
Moved ratings to Review and added Javadoc comments
Unified with Game class
Unified with Account class
Moved logic to Statistics class
Unified with GameStat class

Moved logic from GameStat class to here
Unified with Account class
No more needed
Minor cosmetic change
Implemented with Builder pattern

Also unifies with now-removed AccountInfo class.
Minor cosmetic changes

Changed methods name to start with lowercase.