Improve the api

[Matyrobbrt]

• make CompiledModule ctor public to allow extension, and make some of its methods public final / OverrideOnly
• add an event that allows "hijacking" module execution
• add an event to add data slots to the router (GUI elements can be added via a neo-provided event)
• add UpgradeItem#isCompatibleWith to be able to have an upgrade that can't coexist with another
• add methods to UpgradeItem for client-side syncing
• add a method to ModuleTarget for general capability interaction