test for original "v0" index XML compatibility

The original index.xml format needs to stay around for backwards
compatibility, but we shouldn't touch it anymore once the new format is in
place.  This is a test to make sure `fdroid update` can still generate the
correct XML.

install_list and uninstall_list should be tuples or lists in order to
ensure that the order is preserved.

These tests also check that the added and lastupdated dates are
working correct, based on the dates in tests/stats/known_apks.txt. I
could see no useful way to test the timestamp, it is just hardcoded
using a regexp search-and-replace.  Running these tests manually might
require deleting tmp/apkcache.

examples/config.py

@@ -175,10 +175,10 @@ The repository of older versions of applications from the main demo repository.
 # and the archive, if it is enabled.  So these URLs should end in the
 # 'fdroid' base of the F-Droid part of the web server like serverwebroot.
 #
-# mirrors = {
+# mirrors = (
 #     'https://foo.bar/fdroid',
 #     'http://foobarfoobarfoobar.onion/fdroid',
-# }
+# )
 
 # optionally specific which identity file to use when using rsync over SSH
 #
@@ -253,7 +253,7 @@ The repository of older versions of applications from the main demo repository.
 
 # By default, fdroid will use YAML .yml and the custom .txt metadata formats. It
 # is also possible to have metadata in JSON by adding 'json'.
-# accepted_formats = ['txt', 'yml']
+# accepted_formats = ('txt', 'yml')
 
 # Limit in number of characters that fields can take up
 # Only the fields listed here are supported, defaults shown
@@ -269,13 +269,13 @@ The repository of older versions of applications from the main demo repository.
 # the packageNames listed.  This is protected by the same signing key
 # as the app index metadata.
 #
-# install_list = {
+# install_list = (
 #     'at.bitfire.davdroid',
 #     'com.fsck.k9',
 #     'us.replicant',
-# }
+# )
 #
-# uninstall_list = {
+# uninstall_list = (
 #     'com.facebook.orca',
 #     'com.android.vending',
-# }
+# )