[ NETWORK ] initialize network for conv2d/pooling2d/flatten

[ NETWORK ] initialize network for conv2d/pooling2d/flatten

This PR provides initialization of conv2d, pooling2d, flatten layer
for training configuraion file.

Also modified to update mutiple weights in the optimizer.

**Self evaluation:**
1. Build test:	 [X]Passed [ ]Failed [ ]Skipped
2. Run test:	 [X]Passed [ ]Failed [ ]Skipped

Signed-off-by: jijoong.moon <jijoong.moon@samsung.com>