Added new rule to pattern grammar
    - Allows handling of queries such as AT TILE A;
Refactored calls to WorldTreeFactory to reflect constructor changes
Added TokenOperator class and updated references
Property class now stores an operator instead of hard-coded '='
Updated grammar for boolean conditions
Updated parser to reflect changes made to document
    - Expr
    - AggExpr
Need to implement wrapper classes and return meaningful objects
Tweaked WorldTreeFactory fields and constructors to better accomodate
'World Definitions'
Created separate method to deal with loading definitions
Removed creation of default properties file in constructor
Renamed default definitions file to world.definitions
Updated WorldTreeFactory storage types for properties and definitions
Renamed config to world.definitions
Updated constructor model for PropertyDef to be a lot cleaner
Renamed class TokenOperator to TokenCmpOp
Property class does not store value anymore
Added class TokenArithOp to parser package
Added Expr class and updated Parser
Most WorldTree related classes now implement Serializable
Added empty constructor to Space class to make it deserializable
Rewrote QueryTest class to be more flexible
Updated PropertyDef class to working  condition
Working on AggExpr