[Semantics] InitContext NumOutput is hint

[Semantics] InitContext NumOutput is hint

This patch changes init context num output to be a hint how many outputs
has to be allocated. Layers may or may not depend on this information.
What Layer must gaurantee is that number of acutal outputs must be
bigger than the init context num output requested, this fixes dangling,
unused variable issue

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

Signed-off-by: Jihoon Lee <jhoon.it.lee@samsung.com>