Remove unused File code in libbcc.

Remove unused code from File related classes.  More refactoring to come,
breaking this in small easy to understand steps.

Bug: 34265954
Test: Compiled.  Ran imageprocessing_jb and a compat lab test.
Test: Compared that the APK have not changed in size.
Change-Id: Ic4218b49801d13f0fbbe267516882c150d6d4c93