Singlet links should be supported

[Konard]

It will require removal of pointLink term from grammar. It was added by mistake (when links theory was not ready).

(1) should be interpreted as a link with values list of length 1, with single element 1.

These lines will be deleted:

Protocols.Lino/csharp/Platform.Protocols.Lino/Parser.peg

Lines 21 to 23 in bae8007

	pointLink <Link<string>> = id:(reference) { new Link<string>(id) }
	singleLinePointLink<Link<string>> = __ l:pointLink { l }
	multiLinePointLink<Link<string>> = "(" _ l:pointLink _ ")" { l }

It also may require to rethink how indented whitespace will work with links. For example it may require to create artificial link ids if these not provided, or it may require to throw an error on absent ids.