The text editor and interpreter now use the themes selection color for text selections.
Fixed an issue where the add-tab popup button didn’t list any view extensions.

Previously, PLTabViewController observed the PLAddOnManagerDidLoadNotification in order to update this. Recently, LiasisAppDelegate was changed to load all extensions before any of its views were created; therefore, these notifications were posted before PLTabViewController began observing them. The new approach lazily updates the popup button immediately before displaying the menu so that it is accurate independent of when view extensions are loaded.