`fdroid publish` now includes OTA ZIPs and related source

`fdroid publish` now includes OTA ZIPs and related source

This adds support for publishing ZIP files which were built with
`fdroid build`.  This is for "Over-The-Air" (OTA) update ZIP files for
flashing to ROMs.  The first example of this is the Privileged Extension,
which must be installed by flashing an OTA ZIP on Android > 5.0.

!181
https://gitlab.com/fdroid/privileged-extension/issues/9
https://gitlab.com/fdroid/privileged-extension/issues/10
https://gitlab.com/fdroid/fdroiddata/merge_requests/1804

Also, "if app.Binaries:" is the same as "if app.Binaries is not None:", but
is the standard Python style.