misc: put quote normalization ((quote x) => 'x) in the reader.
datum+proc: remove r5js.Datum#isNonNormalizedQuotation. No longer needed.
misc: inline uses of r5js.Datum#isEmptyList and remove method.
ast: rename r5js.Lambda => r5js.ast.Lambda.
ast: put r5js.ast.Lambda in its own file.
datum: remove no-longer-used r5js.Datum#setImmutableOnQuote.