Add Character Support to the assembler.

[gilkeidar]

Added a new TokenType: TokenType::CHARACTER.

Can specify a Character token using the new OUT Assembly Instruction; hence, the following code:

// First, painstakingly define preprocessor constants for each character value.
// Note: these could be hardcoded into the assembler, but this would introduce a lot of reserved constants values
// that aren't necessarily obvious to be built-in constants; additionally, they're less readable than built-in characters.
.define 1 NEW_LINE 0x10
.define 1 SPACE 0x20
.define 1 _A 0x41

// Print " A\n"
OUT SPACE, A
OUT _A, A
OUT NEW_LINE, A

Can be replaced with the following new code:

// Print " A\n"
OUT ' '
OUT 'A'
OUT '\n'

As you can see, special characters (that are escaped using \) have also been added, and largely follow C's set of escaped characters.

Closes #3