Multiple fixes

* Multiple fixes:

 * [OPENNAAS-1149](http://jira.i2cat.net/browse/OPENNAAS-1149)
 * [OPENNAAS-1150](http://jira.i2cat.net/browse/OPENNAAS-1150)
 * [OPENNAAS-1154](http://jira.i2cat.net/browse/OPENNAAS-1154)
 * [OPENNAAS-1169](http://jira.i2cat.net/browse/OPENNAAS-1169)
 * [OPENNAAS-1170](http://jira.i2cat.net/browse/OPENNAAS-1170)

* Added new message factories (ErrorFactory and ReplyFactory)
* Serializable `Reply` implementing `toXml()`