Improve examples in javadoc of *Feed

- For FunctionFeed, HttpFeed, ShellFeed, SshFeed and JmxFeed
- Example puts feed in context, of an entity extending 
  SoftwareProcessImpl
javadoc in *Feed: incorporate review comments

- Use {@literal @}Override in code sample so the @ isn't interpreted
  strangely.
- But that only seems to work if there was a "}" immediately before the
  @Override
- So just being lazy and doing //@Override in the first case.
Merge pull request #562 from aledsage/fix/Feed-javadoc-examples

Improve examples in javadoc of *Feed