Add color schemes and character sets

[theNestruo]

Add color schemes and character sets.

Color schemes:

• default: Default monochrome (mimics original extension)
• rainbow and rainbowLight: Color choosen by high nibble
• categories and categoriesLight: Color choosen by category (non-printable ASCII, printable ASCII, non-ASCII)
• gradient: Color gradients

Character sets:

• dot: Renders a regular dot
• middot: Renders a middle dot (lighter than a regular dot)
• bullet: Renders a bullet
• cross: Renders a cross (a multiplication sign)
• symbol: Renders a glyph that represents the control code
• ascii: Renders the actual ASCII character
• braille: Renders a braille glyph based on the byte value

Category	dot	middot	bullet	cross	symbol	ascii	braille
nonPrintableAscii	dot*	middot*	bullet*	cross*	symbol		braille
printableAscii						ascii	braille
nonAscii	dot	middot	bullet	cross			braille

* Particularly relevant characters (NUL 0x00, TAB 0x09, LF 0x0A, CR 0x0D, whitepace 0x20, and DEL 0x7F) will use their own glyphs

Screenshot:

Color schemes fulfil the feature request: #597