Big update, mostly security

[MKGirlism]

Since the ownership of this site was transferred from DZ to me, the IP.Services software was really lacking behind, when it comes to updating.
I initially didn't bother getting a license, because my plan was (and actually still is) to switch to my custom forum system, once it's ready enough for this community.

However, since it'll still take a while before the time comes, and figured out I could still renew my IP.Services license I dropped 2 years ago for way cheaper, I figured it would be better to do that in the meantime, so we could apply all the security patches for now (and jump from 4.9.16.2 all the way up to 4.9.19.4).

I personally don't expect a lot of changes from a regular users' perspective, but who knows?