x64 support via <virtual_address>

[Malifox]

Requires 1.13.0.7278 or greater. No breaking changes and I didn't find any compatibility issues. For 64-bit servers with plugins that rely on tf2attributes, as long as the plugin doesn't directly load address values(ex: LoadFromAddress()), then it should work as is without needing a recompile to include <virtual_address>.

Also included is a testing plugin to test all current natives with a single sm_test_tf2attributes command. I had a slight whitespace mishap when it came time break things into smaller commits that I'm hoping can be rebased out easily enough.

This solves #50

[FlaminSarge]

Would it be worth me removing all the trailing spaces and you rebasing so that they aren't a part of this PR?

[Malifox]

If you find that to be the simplest method and don't mind the loss of those _^evil whitespaces, I otherwise didn't mess up the formatting and that should work out. I didn't disable auto trim on save when I worked on this and I discovered the error of my ways after nearly everything was written. With quite a few changed lines needing be broken up into commits, the "I'll figure it out later" idea sounded good, at least at the time. Which of course left me with a bunch of whitespace diffs I don't know what to do with.

Other things of note, I left in the complete offsets layout for the used classes, which I found very useful in other places and aren't too likely to change at this point. Could be easily trimmed out if you find that it bloats things too much though.

[FlaminSarge]

load-bearing whitespace

I'll go ahead and strip all of those from master branch and see how close I can get to your diff having no whitespace changes, and then have you rebase on top of that; hopefully that won't be too painful.

[Malifox]

Something else to consider is that this can currently only be loaded on 1.13.0.7278+, the LoadAddressFromAddress() and StoreAddressToAddress() natives and public const Address PointerSize do not exist in the stable 1.12 branch, which complicates moving to this a bit actually.