Spit and shine

This was a big week of little things! We added two features:

• Line numbers in the editor. (You can turn them off).
• Allowing + to be a unary operator.

We fixed more than two dozen issues, including:

• Improvements to text cursor placement in localized code
• Control over the language used to evaluate a program
• Improvements to localization of code
• Color accessibility improvements
• Fixed a few cases where projects ended up with the wrong owner
• Improved emoji rendering in Safari
• Improved localized rendering of tooltips