ENH: Builder code comp open to first non-blank page

I love the tabs!
- now code comp opens to first non-blank flatnotebook page
- larger text area for rating-scale customize-everything box
FF: code component open-to-page

- could get page -1 if had some code then deleted it (fixed by max)
- ignore whitespace for purposes of selecting the page
Merge pull request #475 from jeremygray/master

Builder code component now opens to the first non-blank tab