[omemo] Update manifest.ini & CHANGELOG

omemo/CHANGELOG

+2.6.57 / 2019-03-26
+- Refactoring
+
 2.6.56 / 2019-03-25
 - Fix database version
 

omemo/manifest.ini

 [info]
 name: OMEMO
 short_name: omemo
-version: 2.6.56
+version: 2.6.57
 description: OMEMO is an XMPP Extension Protocol (XEP) for secure multi-client end-to-end encryption based on Axolotl and PEP. You need to install some dependencies, you can find install instructions for your system in the Github Wiki.
 authors: Bahtiar `kalkin-` Gadimov <bahtiar@gadimov.de>
  Daniel Gultsch <daniel@gultsch.de>