Closes #4 with new param LAST_VALID_TAGS_COUNT

[ryttuo]

Added LAST_VALID_TAGS_COUNT param so you can set last N tag version to keep into the registry, for instance if the registry has:

https://:5000/:1.0.10
https://:5000/:1.0.9
https://:5000/:1.0.8
https://:5000/:1.0.7
https://:5000/:1.0.6

If LAST_VALID_TAGS_COUNT = 3 after run script the result should be:

https://:5000/:1.0.10
https://:5000/:1.0.9
https://:5000/:1.0.8

Other tags without numbers keep the same approach removed after MAX_AGE_SECONDS