Correctly detect IE11 in the `Environment::agent()` method (see #6378)
Correctly handle "includeBlankOption" and numeric columns (see #6373)
Fixed the ACE version number and added an inverted theme (see #6101)
Change the default back end font color from `#666966` to `#555`
Use CSS classes instead of style attributes to colorize the theme importer messages
Adjust the colored fonts to the new text color