Support CompletionItemKind.Method

[sandyarmstrong]

Previously, if a registered completion provider returned items with
CompletionItemKind.Method, they would display in the list as properties,
due to not being converted to the corresponding SuggestionType.

[msftclas]

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[sandyarmstrong]

I was thinking of doing the same in MyCompletionItem.convertKind (for case PConst.Kind.memberFunction), but I'm not as familiar with that area of the code.

[jrieken]

LGTM