gitk: use headoutlinecolor, headbgcolor, and tagfgcolor config settings to change the color of the tags and head outlines and fill #2030

MagmaiKH wants to merge 1 commit intogitgitgadget:mastergitgitgadget/git:masterfrom

MagmaiKH:sbarber/use_color_config_variablesMagmaiKH/git:sbarber/use_color_config_variablesCopy head branch name to clipboard