CompletionItemKind missing some kinds from SymbolKind

[smarter]

I don't get why CompletionItemKind does not extend SymbolKind since you can presumably complete any kind of symbol. In any case, it would be nice if CompletionItemKind provided Namespace or Package since that's a common thing to want completion on.

[felixfbecker]

I wondered that too! The set of completion items should be a super set of the set of symbol kinds. It makes no sense that there are symbols that cannot be provided for completion, since the editor would already have the icons for it anyway.

[dbaeumer]

The difference is:

	export const Namespace;
	export const Package;
	export const Constant;
	export const String;
	export const Number;
	export const Boolean;
	export const Array;

I am not sure how useful it is to have String, Number, Boolean and Array as CompletionItemKind. But it doesn't hurt either.

@jrieken can you recall any reasons why we kept them so different.

[felixfbecker]

I am particularly interested in Namespace

[jrieken]

Yeah, no particular reason. Mostly historical reasons, something we can revisit

[dbaeumer]

OK. Great.

[dbaeumer]

Dups #129