Post-patch 5 version improvements

[adamd3v]

This PR features some fixes for very annoying bugs. It fixes the elements disappearing when there are too many on a page, and a few other issues. Below is a full list of everything that has changed.

Codebase

• Code consistency updates
• Changed HandNotificationData and HeadNotificationData to be a class instead of a struct
• All action invokes use InvokeActionSafe
• Removed Menu.CreatePage as page creation is a responsibility given to pages
• Property changes: Any set accesses made to element properties now invokes actions when the element gets updated
• Events in classes now have internal callbacks, so they don't get invoked by other code that isn't this mod
• Page's root set accessor made internal for security
• Removed layout type as it is unneeded this version
• Rewrote some code that used LINQ operations (finding assemblies and clearing out active elements)

Menu

• Fixed an issue with the scroll view sending elements into high-Earth orbit
• Increased scroll speed
• Improved the look of the background, and moved it closer

[FirEmerald]

I realize I'm rather late to say this but Menu.CreatePage should not have been removed, but rather marked for deprecation. Removal of the method broke some of my mods with zero warning, and there really was no reason to remove it entirely. I'm glad it's an easy fix but outside of major version changes, API method changes or removals should be kept to a minimum.