[ModelLoader] Use vector<string> when create layer

[ModelLoader] Use vector<string> when create layer

When creating a layer from an ini, enum based properties were used.
This prevents adding a new properties without changing the api header.

This patch moves to setting layer properties to vector<string>
to enable setting properties without changing the api header, eventually
 enabling custom properties in custom layer.

**Semantics Change propesed in this PR**
Ini won't ignore the properties that is not supported since model_loader
would not know if it is supported or not

See also #716

**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>