Improve plugins

[danielbrendel]

Improve array plugin:

• Allow arrays to store objects such as class instances
• Allow resize command to clear an array if the size value is zero
• Use array_ prefix for all array commands for better overview

Improve DirectX plugin:

• Fix that Renderer key and mouse methods fail to determine bDown and other control keys
• Allow sound plugin to specify whether a sound shall be looped or not

[danielbrendel]

Improve Forms plugin:

• Creating and managing image boxes does not work
• Setting and initial image shouldn't be mandatory for image boxes
• Add event handlers OnChange for text input elements
• Add event callback script functions for imagebox: onclick, onmouseover and onmouseleave
• Add MsgBox command with title, caption, buttons, HWND and return value
• Add commands for GetOpenFileName and GetSaveFileName

[danielbrendel]

Improve events plugin:

• Add events.exists command to check if an event exists

Improve auto plugin:

• Add command for keybd_event
• Add command for mouse_event