[manager] Added nntrainer manager for weights

[manager] Added nntrainer manager for weights

Added manager to manage all the allocated weights
This patch also adds manager to the model and passes manager to the
initialize which allows weights to be added to the manager.

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

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