export enumeration definition to ssp

[arun3688]

Related Issues

#1259

Purpose

This PR implements exporting enumeration definition to ssp according to SSP standard

example

<ssd:Enumerations>
  <ssc:Enumeration
    name="Modelica.Blocks.Types.LimiterHomotopy">
    <ssc:Item
      name="Linear"
      value="2" />
    <ssc:Item
      name="LowerLimit"
      value="4" />
    <ssc:Item
      name="NoHomotopy"
      value="1" />
    <ssc:Item
      name="UpperLimit"
      value="3" />
  </ssc:Enumeration>
</ssd:Enumerations>