Conway's Game Of Life with multiple species

php gol.php inputfile.xml

• square world n×n
• m species
• 8 surrounding cells (straight and diagonal)
• organism surrounded by <2 same-species organisms: dies
• organism surrounded by 2-3 same-species organisms: survives
• organism surrounded by >3 same-species organisms: dies
• empty cell surrounded by 3 same-species organisms: new organism
• two organisms at one cell: random one survives, other dies

• species do not influence each other (except when conflicted)
• coordinates are 0-based, increasing (e.g. n=10 gives a 100-cell grid from [0,0] to [9,9])
• invalid data (e.g. outside grid) are rejected with the whole import (dropping them is another option, I don't think either of these is universally applicable)

• GolApp checks the XML filename passed as argument
  • instantiates XmlBoardImporter, which imports the XML into a LifeBoard
  • instantiates LifeBoardCalculator
    • passes it the LifeBoard of current generation
    • LifeBoardCalculator goes through the LifeBoard and calculates what lives and what dies
    • returns new LifeBoard with new generation back
    • repeat calculation until LifeBoard->maxGenerations elapsed
  • calls XmlExporter->export() of LifeBoard to write the result to a XML