Master Issue for Updating Color/Attribute System

[tig]

This is the master Issue for revamping the Color system in v2. Dependencies:

• Revamp built-in Scheme's (e.g. what *is* Toplevel anyway?). #4086
• Fixes #4057 - MASSIVE! Fully implements ColorScheme->Scheme + VisualRole + Colors.->SchemeManager.  #4062
• Rename ColorScheme to Scheme and Migrate Colors to ConfigurationManager.Themes #4057
• Add Non-Color Attributes (Bold, Italic, Underline, etc.) to Attributes #4058
• Attribute System Should honor terminal settings #2381
• Refactor Color/True Color - Make TrueColor default #2797
• Add TrueColor support to CursesDriver #2798
• Add TrueColor support to NetDriver #2799
• Attributes: Support Bright/Bold, Dim, Underline, Blink, Reverse, Hidden, and Strike-through  #219
• Update ColorPicker for TrueColor #2801
• Revamp ColorPicker and Color Scenarios in UICatalog #2800

See also:

• Colors: The native method "COLOR_PAIRS" does not exist #415

[tig]

The fix for #666, PR #2612 is providing groundwork for this. Anyone choosing to start on this PR should base it on that PR if you do it before merged in to v2_develop.

[adstep]

Hey @tig, is #2612 still the right branch to start from if I'm playing around with porting over the changes from #1628?