[ini] Update Network section to Model

[ini] Update Network section to Model

Update section name from Network to Model
Also update internal naming in loadModel and correspondingly unittests

Resolves #318

**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>