[layer] refactor num of inputs/outputs

[layer] refactor num of inputs/outputs

Refactor layer to properly handle the number of inputs
and outputs, which is maintained across the in/out dimensions,
in/out data.
This is not maintained for in/out layers as these properties will move
out of layers in the next commit.

Also added bugfix in output_layer which used to clear the output dimension
rendering the num outputs 0 for sometime.

NetworkGraph setNumNetBufferSize is also removed as the above
refactoring handles it at the layer level.

See Also #986

Signed-off-by: Parichay Kapoor <pk.kapoor@samsung.com>