ConnGrowth::updateSynapsesWeights method on GPU must be redesigned

[fumik]

See #221

[fumik]

Now we use multi-GPUs on ConnGrowth::updateConnections() method.

1. Eliminates CompleteMatrix W, delta, area and VectorMatrix outgrowth, deltaR. These data areas were used to save temporary results and occupied a lot of memory. Now these data areas are moved to temporary variables in kernel functions.
2. Changed ConnGrowth::updateConns() method to updateConnsDevice() kernel function.
3. Integrated ConnGrowth::updateFrontiers(), updateOverlap() and updateSynapseWeight() methods into updateSynapseWeightDevice() kernel function.
4. Changed CompleteMatrix radii and rates to arrays so that it is easier to transfer data between GPU and CPU memories.

performance data_2.xlsx