Add configurable max_hamming_distance for the AprilTag Detector

[akshayprsd]

Adds configurable max hamming distance bits for the AprilTag Detector.

Context:

1. Noticed high memory usage for the 52h13 family detector.
2. Noticed that apriltag_ros initiates the apriltag detector with max_hamming_distance value of 2 bits by default which is hardcoded in the apriltag library.
3. Noticed that reducing the max_hamming_distance bits from 2 to 1 brings down memory usage drastically.
4. Added configurable ros param to be able to configure this value.

I might have missed some documentation files which might need to be updated. Happy to take a look at those.

[akshayprsd]

@wxmerkt Can we get this merged if its good to go?

[wxmerkt]

I added comments on the parameter setting from upstream which are now passing through the buildserver. I am not certain if there isnt a loss of quality of detection reducing the setting? How much was the memory usage before/after?

[akshayprsd]

The memory usage drops from about ~6 GB for the 52h13 family to ~ 200 MB.

int capacity = family->ncodes; // 48714
int nbits = family->nbits;
if (maxhamming >= 1)
   capacity += family->ncodes * nbits; // 48714 + 48714 * 52
if (maxhamming >= 2)
   capacity += family->ncodes * nbits * (nbits-1); // 48714 + 48714 * 52 + 48714 * 52 * 51
qd->nentries = capacity * 3; // (48714 + 48714 * 52 + 48714 * 52 * 51) * 3
qd->entries = calloc(qd->nentries, sizeof(struct quick_decode_entry)); // (48714 + 48714 * 52 + 48714 * 52 * 51) * 3 * 12

So memory allocated = (48714 + 48714 * 52 + 48714 * 52 * 51) * 3 * 12 = 4743769320 bytes ~ 4.73 gigabytes with max_hamming_distance = 2.

For max_hamming_distance = 1 -> ((48714) + (48714 * 52)) * 3 * 12 = 92946312 bytes ~ 92 MEGAbytes.

If we reduce the max_hamming_distance it should increase the accuracy as we are allowing fewer bit errors to be looked up. However some valid detections might dropped because we are allowing fewer errors.

Irrespective I think being able to configure the parameter is valuable and we retain the original functionality by setting 2 as the default parameter.

[wxmerkt]

Thank you for the detailed explanation and contribution. :-)