Save prekeys optimistically, track confirms, new clean behavior (#1846)

* Re-enable libtextsecure unit tests, get passing, run in CI

* Save prekeys optimistically, track confirmed, new clean behavior

* Eliminate potential conflicts when rotating on startup

* Remove last symlink: get libtextsecure tests running on windows

config/test-lib.json

@@ -0,0 +1,5 @@
+{
+  "storageProfile": "test",
+  "disableAutoUpdate": true,
+  "openDevTools": false
+}