Compatibility with cordova-plugin-file@7 Android URLs

Hi there,

the new release 7.0.0 of `cordova-plugin-file` changed the format of URLs generated via `file.toURL()` and `file.toInternalURL()` from `cdvfile://localhost/persistent/...` to `https://localhost/__cdvfile_persistent__/...` on Android. This plugin does not seem to be able to handle them yet.

As a workaround, I am currently using `file.nativeURL`, which seems to work quite well.

Thanks for looking into it!

Start by reproducing the issue with cordova-plugin-file@7 on Android, comparing file.toURL() and file.toInternalURL() output with the formats described in the report. Trace where this plugin handles cdvfile:// and https://localhost/__cdvfile_persistent__/ URLs; done means the new Android URLs work without requiring file.nativeURL.

Written by the indexing model from the issue text.