text: Title: [FEATURE] Rename the limit method to take. Add it in Fugue SQL
  Body: **Context**
  The limit method pull request is close to being [merged](https://github.com/fugue-project/fugue/pull/131). This method should be renamed to `head` because there already is a ANSI SQL keyword named `LIMIT`. After renaming this to `head`, implement the `HEAD` keyword for Fugue SQL with the same parameters as the execution engine definition.
  