Move incomplete colorschemes and improve cd

The default colorschemes should ideally use 256 colors instead
of just 16 colors. The `simple` colorscheme should cover most
16 color use cases. I went through the colorschemes and put the themes
that didn't look good or looked incomplete in an in_progress directory.

This commit also improves the `cd` command behavior when using an
unnamed buffer.

runtime/syntax/go.yaml

@@ -11,11 +11,9 @@ rules:
     - symbol.operator: "[-+/*=<>!~%&|^]|:="
 
       # Types
-    - special: "[a-zA-Z0-9]*\\("
     - symbol: "(,|\\.)"
     - type: "\\b(u?int(8|16|32|64)?|float(32|64)|complex(64|128))\\b"
     - type: "\\b(uintptr|byte|rune|string|interface|bool|map|chan|error)\\b"
-      ##I'm... not sure, but aren't structs a type?
     - type.keyword: "\\b(struct)\\b"
     - constant.bool: "\\b(true|false|nil)\\b"