2.0.12 beta

Features

• Add scss/variables folder with SCSS skin variables for easier import
• Add variable map for generic variables, accessible with const()
• Add toggleMode to the API with optional boolean state enforcer, used like this:

    import Theme from 'nativescript-theme-core';

    Theme.toggleMode(); // to toggle between the modes

    // or

    Theme.toggleMode(true);  // to ensure dark mode
    Theme.toggleMode(false); // to ensure light mode

Fixes

• Fix dark mode for Switches and several other components
• Fix ActionBar Label title background, fix dark buttons
• Fix the colorize function to produce better organized code, to work with consts and to properly
  prepend .ns-dark on root classes