beremiz

WIP: Add skeleton for MQTT extension based on part of OPC-UA extension.

For now generated code makes no sense but persistently-configurable-C-generating-extension infrastructure is there.
<xsd:attribute name="Command" type="xsd:string" use="optional" default="make -C %(buildpath)s -f ../project_files/Makefile all BEREMIZSRC=%(src)s BEREMIZCFLAGS=%(cflags)s MD5=%(md5)s USE_BEREMIZ=1 FROM_BEREMIZ=1"/>