[Filesystem] Fix and complete the API

Implement the spec.
Fix and pass the TCT tests.
Fix and complete the example.

BUG=XWALK-1071
BUG=XWALK-1827
how this list come from? If it comes from iconv library/command, I have two solutions instead of host the huge list:
1. Do action in GYP and generate a .js and combine them in someway.
2. Get the list in native code in someway, and PostMessageToJS on initialization stage.