Added Light base class and refactored spherical light to point light source
Refactored shape to remove lighting code, updated point light to support new light interface
Refactored functions for adding shapes and added new functions and list for lights
Updated recursive strategy to include lights list
Updated engine to pass lights to the trace strategy
Fixed compile errors
Refactored recursive trace to use new lighting model
Added Light base class to compile list
Updated spheretest to use new lighting model
Changed pass-by-reference to multiple return values using pair for intersection function
Merge branch 'master' of ssh://github.com/Queuecumber/RealRT
Added out_of_range exception for bad vector subscript accesses
Added empty return from iterate strategy for the time being to fix compile warning