[Tizen] Native File System API

Completed features list:

Create file
Read file
Write file
Remove file
Create Directory
List Directory Entries
Remove Directory

BUG=https://crosswalk-project.org/jira/browse/XWALK-1875
This variable is required for 
```
          'cflags': [
            '<!@(<(pkg-config) --cflags libtzplatform-config)',
          ],
          'link_settings': {
            'libraries': [
              '<!@(<(pkg-config) --libs libtzplatform-config)',
            ],
          },
```
Add you can refer to media.gyp or system.gyp. These gyp files also define pkg-config variable.