pySim-shell: Add a "version" command to print the pySim package version

It may be interesting to know which pySim-shell version a user is running.

Change-Id: Ib9a1fbff71aa8a2cfbaca9e23efcf7c68bf5af1a
Closes: OS#5459

pySim-shell.py

@@ -447,6 +447,11 @@ class PysimApp(cmd2.Cmd):
         """Echo (print) a string on the console"""
         self.poutput(opts.string)
 
+    @cmd2.with_category(CUSTOM_CATEGORY)
+    def do_version(self, opts):
+        """Print the pySim software version."""
+        import pkg_resources
+        self.poutput(pkg_resources.get_distribution('pySim'))
 
 @with_default_category('pySim Commands')
 class PySimCommands(CommandSet):