Parser now parses multiple words into constant()
Parser implementation of MAXMIN in expr() is incorrect
    - Added a FIXME
Added evalulate() methods to IExpr and ICondition
    - TODO: To be moved elsewhere to maintain clean separation
      between hierarchy classes and containers
Updated QueryResolutionEngine to use Hierarchy enum

QueryResolutionEngine.getObjects() now begins from node.parent()
if node is on the same level as the objects requested
Added new example to sample directory
    - simple_inbuilt_relation
Working on solver for conditions and expressions