cItem: Store custom data

[NiLSPACE]

I'd be great of we could just do something like this:

item.m_ItemMeta = 
{
	author = "NiLSPACE",
	title = "Cuberite\'s darkest secrets",
	pages = 
	{
		"Cuberite was previously called MCServer",
		"While Cuberite is hosted on Github it used to be hosted on code.google.com",
		"These are not dark secrets"
	}
}