Remove BalanceTree ; add new doc

Obsolete/BalancePerfTest.cpp

Obsolete/BalanceTree/FAbstractBalanceAlgorithm.hpp

Obsolete/BalanceTree/FChebSymCostKernel.hpp

Obsolete/BalanceTree/FCoordColour.hpp

Obsolete/BalanceTree/FCostCell.hpp

Obsolete/BalanceTree/FCostZones.hpp

Obsolete/BalanceTree/FDumbCostKernel.hpp

Obsolete/BalanceTree/FEqualize.hpp

Obsolete/BalanceTree/FFmmAlgorithmThreadBalanced.hpp

Obsolete/BalanceTree/FLeafBalance.hpp

Obsolete/BalanceTree/FParticlesBalance.hpp

Obsolete/BalanceTree/FPartitionsMapping.hpp

Obsolete/testFmmAlgorithmBalanced.cpp

Obsolete/testInsert.cpp

Obsolete/testTreeBuilder.cpp