Introduce bold color option

Introduce "bold" color option which only apply bold color formatting to
existing system color.

Also make "bold" the default color option.

Fixes all white issue with black on white tio text.

src/configfile.c

@@ -226,6 +226,12 @@ static int data_handler(void *user, const char *section, const char *name,
                 return 0;
             }
 
+            if (!strcmp(value, "bold"))
+            {
+                option.color = 256; // Bold
+                return 0;
+            }
+
             option.color = atoi(value);
             if ((option.color < 0) || (option.color > 255))
             {