Implement dedicated plugin handling

[LobaDK]

Currently, the main application code is responsible for managing the whole plugin loading process.

To further abstract and separate them, the plugin SDK should solely be responsible for any and all plugin related events, including at minimum the following:

• Scanning and loading plugins
• Registering their handlers
• Invoking/Running any async or separate process/thread

Additionally, for future enhancement, the following can be considered:

• Unloading plugins
• Atomic reloading of plugins (If loading fails for whatever reason, the existing/previous state is restored)
• A system for inter-communication between the plugins, allowing them to talk to (query?) each other