Bat already has a base16 theme. The new base16-256 theme is for users
of base16-shell, who configure their terminal with a 256-color variant
of a base16 theme. These variants put some of the base16 colors in
elsewhere in the 256-color table to avoid clobbering bright color slots
(ansi codes 8 to 15) with colors that don't respect the ordinary meaning
of that slot (e.g. bright green in ordinary base16 is not green).
For more details, see https://github.com/chriskempson/base16-shell
This changes the base16 theme back from #RRGGBB0f to #RRGGBB00,
reverting part of #934. That PR used the 0f encoding to produce ANSI
escape sequences 30-37 and 40-47 rather than 38;5 and 48;5 which require
256-color support. Unfortunately, it resulted in base16 using the wrong
colors becuase ansi_term does not support the bright variants (90-97 and
100-107) so it simply mapped them to the non-bright colors.
This PR makes combines the 00 and 0f alpha encodings into 00, and makes
them use the Color enum for the first 8 colors and Fixed otherwise. This
means the ansi-light and ansi-dark themes will work on terminals without
256-color support, and base16 will render bright colors correctly.
