use private / secure local storage for .ts files

[trasa]

Rather than saving the files to a local directory, it'd be 'neat' to have an option to save the .ts files to a secure storage location on the device.

[trasa]

In commit 1e1555e I copied the .ts file from where it was buried in app-data (and not easily browsable by the user) and move it to the phones media folders. Much easier to locate that way.

Having an option to (instead) write the file to the secured storage would still be a nice-to-have.