RPM Support

Each collection can have 0 or 1 module in it.
Module contains an NSVCA info about itself.

Extend UpdateRecord model and serializer to have an optional filed module

<pkglist>
  <collection short="">
     <name>coll_name1</name>
     <module name="kangaroo" stream="0" version="20180730223407" context="deadbeef" arch="noarch"/>
     <package arch="noarch" name="kangaroo" release="1" src="http://www.fedoraproject.org" version="0.3">
        <filename>kangaroo-0.3-1.noarch.rpm</filename>
     </package>
  </collection>
  <collection short="">
     <name>coll_name2</name>
     <module name="duck" stream="0" version="20180730233102" context="deadbeef" arch="noarch"/>
     <package arch="noarch" name="duck" release="1" src="http://www.fedoraproject.org" version="0.7">
       <filename>duck-0.7-1.noarch.rpm</filename>
     </package>
  </collection>
</pkglist>