converts functions to poroperties where applicable (#29)

[LostMekka]

Fixes #29.

Changes:

• Optimizer
  • fun getOptimizerName() -> val optimizerName
  • fun isRunningOnGPU() -> val isRunningOnGPU
• Layer
  • fun getParams() -> val paramCount
  • fun hasActivation() -> val hasActivation
  • fun getWeights() -> fun extractWeights()
• Dense
  • fun getKernelShape() -> val kernelShapeArray
  • fun getBiasShape() -> val biasShapeArray
• Conv2D
  • fun getKernelShape() -> val kernelShapeArray
  • fun getBiasShape() -> val biasShapeArray

[LostMekka]

@zaleslaw I was not sure about the changes in Dense and Conv2D. There were name collisions with private properties, so I renamed the public ones. I could also rename the private ones instead to keep the API cleaner...

I also chose the name extractWeights for now, but this can of course be changed 😃

[zaleslaw]

Dear @LostMekka could I advise you to convert extractWeights to property 'weights' with getter, long body of getter could be extracted to the separate function with name 'extractConv2DWeights' for example?
Will it became cleaner?

[zaleslaw]

All previous changes could be merged, but maybe we achieve more for weights getters

[LostMekka]

OK, I have converted extractWeights to a property as well :)