Add -l option for adjustable block deletion

[gnbon]

• Introduce the -l option to set min block deletion length using powers of 2 (e.g., 1, 2, 4, 8, 16, ...).
• This enables a trade-off between minimization thoroughness and speed.
• Adjusting del_len_limit allows for faster processing, as doubling it roughly halves the minimization time.
• Closes #431

[ifratric]

Great, thanks!