Bump version to 0.15
[Common] Fix IO_ERR message

FileSystem TCT Test "File_readAsText_with_onerror.html" requires
that the error message can't be null.

code:
  assert_not_equals(error.message, "", "incorrect error message");
[FileSystem] Fix ConvertFrom() 64bits decode algorithm
[FileSystem] Add FileStream fstream support

Before this fix, FileStream used FileDescriptor to access its files.
We had some problems dealing with the position attribute, so we
decide to look how tizen deals with it. Tizen uses fstream to handle
the FileStream class, so as we do now.