Added development.com.collection.range package

This package consists of classes that implement the concept of
Ranges

Consists of two classes that extend the abstract class Range
    - IntegerRange
    - FloatRange

Currently, Ranges allow the following functionality
    - contains
    - intersection
    - add
    - span
    - generateRandom
    - clone

Range addition currently works only for the same types

PropertyDef.RandomSpec now uses Range class
Updated Parser and WorldTree to reflect this change

WARNING: This patch breaks the existing WorldTree.split method
Added small but necessary check in pushDownConstraints break case
Moved Tile's string methods so that they all appear together

Tile.updateVisuals method reloads artifacts everytime
However, artifacts was not being cleared
This led to same property being displayed several times per tile

Added artifacts.clear() to Tile.updateVisuals
Working on Hierarchical split

Updated Hierarchical split so that bounds are handled correctly for sum