Data analysts should be able to use Text.split, Text.lines and Text.words to break up strings

[radeusgd]

Pull Request Description

Implements https://www.pivotaltracker.com/story/show/181266184

Important Notes

Changed example image download to only proceed if the file did not exist before - thus cutting on the build time (the build used to download it every time - which completely failed the build if network is down). A redownload can be forced by performing a fresh repository checkout.

Checklist

Please include the following checklist in your PR:

• The documentation has been updated if necessary.
• All code conforms to the Scala, Java, and Rust style guides.
• All code has been tested:
  • Unit tests have been written where possible.
  • If GUI codebase was changed: Enso GUI was tested when built using BOTH ./run dist and ./run watch.

[jdunkerley]

Generally looks good - a couple of bits to just look over