Issue: Remove Support for vBulletin 3

While debugging today, I discovered a major showstopper in VaultWiki under vBulletin 3, where it is not possible to edit any forum settings without receiving a fatal error. Due to the severity of the issue, and the length of time the bug has existed (close to a year and a half), the only way it has gone unreported for so long is if we have close to zero active clients using VaultWiki in a vBulletin 3 environment. This is a question we have had for some time, and this discovery seems to confirm our suspicions.

Because of this, it seems that maintenance of vBulletin 3 support (which includes over 400 style templates) is not a good use of resources. In the next branch, VaultWiki 4.2.x, we should remove separate support for vBulletin 3 (aside from upgrades and imports coming from vBulletin 3). Furthermore, for the future of the 4.1.x and 4.0.x branches, vBulletin 3 will not receive any additional features or improvements that require templating, aside from bug fixes (assuming any are reported). This will save a lot of development time for improvements that actually benefit the other ~100% of clients.