Implement bit test instruction BIT

BIT tests whether the result of an 'and' between the accumulator and a value in memory is 0, storing the value in the Z (zero) flag. It also sets the N (negative) flag to bit 7 of the value in memory, and the V (overflow) flag to bit 6.

[Reference](http://www.obelisk.demon.co.uk/6502/reference.html#BIT)