Allow passing varargs from vgui.Create to Panel:Init

[luca1197]

This PR makes it possible to pass varargs from vgui.Create to Panel:Init for custom (user-created) panels.

Passing arguments to Panel:Init can be quite useful in a few cases, generally when the goal is to allow changing some behavior in the Init function without it being really necessary to separate these different behaviors into individual functions.

It would be possible to define a custom init function for the panel and call that after vgui.Create, but I don't see a reason why a cleaner solution like this shouldn't exist.

Thanks :)

[darkfated]

A conditional constructor that allows arguments to be passed during initialization... In the context of GLua, this can cause confusion, because it is not known which of the ui elements has support for this, and the elements for which things we transmit. It is better to adhere to encapsulation, and formalize everything through methods. A useless thing

[luca1197]

I see what you're saying, but in my opinion the goal should be to allow different implementation "styles" for the many possible use-cases. If you prefer not to make use of it, that's totally fine, but the option remains available for those who do. Especially since this is just a minor change that applies only to panels that explicitly choose to make use of it.