feat(templates): introduce quoted expressions to support 3rd-party expression languages

A quoted expression is:

quoted expression = prefix `:` uninterpretedExpression
prefix = identifier
uninterpretedExpression = arbitrary string

Example: "route:/some/route"

Quoted expressions are parsed into a new AST node type Quote. The `prefix` part of the
node must be a legal identifier. The `uninterpretedExpression` part of the node is an
arbitrary string that Angular does not interpret.

This feature is meant to be used together with template AST transformers introduced in
a43ed79ee7. The
transformer would interpret the quoted expression and convert it into a standard AST no
longer containing quoted expressions. Angular will continue compiling the resulting AST
normally.

modules/angular2/test/core/change_detection/parser/parser_spec.ts

@@ -230,6 +230,15 @@ export function main() {
           expectBindingError('"Foo"|1234').toThrowError(new RegExp('identifier or keyword'));
           expectBindingError('"Foo"|"uppercase"').toThrowError(new RegExp('identifier or keyword'));
         });
+
+        it('should parse quoted expressions', () => { checkBinding('a:b', 'a:b'); });
+
+        it('should ignore whitespace around quote prefix', () => { checkBinding(' a :b', 'a:b'); });
+
+        it('should refuse prefixes that are not single identifiers', () => {
+          expectBindingError('a + b:c').toThrowError();
+          expectBindingError('1:c').toThrowError();
+        });
       });
 
       it('should store the source in the result',
@@ -414,7 +423,7 @@ export function main() {
       it("should throw when the given expression is not just a field name", () => {
         expect(() => parseSimpleBinding("name + 1"))
             .toThrowErrorWith(
-                'Simple binding expression can only contain field access and constants');
+                'Host binding expression can only contain field access and constants');
       });
 
       it('should throw when encountering interpolation', () => {

modules/angular2/test/core/change_detection/parser/unparser.ts

@@ -18,6 +18,7 @@ import {
   LiteralPrimitive,
   MethodCall,
   PrefixNot,
+  Quote,
   SafePropertyRead,
   SafeMethodCall
 } from 'angular2/src/core/change_detection/parser/ast';
@@ -187,5 +188,7 @@ export class Unparser implements AstVisitor {
     this._expression += ')';
   }
 
+  visitQuote(ast: Quote) { this._expression += `${ast.prefix}:${ast.uninterpretedExpression}`; }
+
   private _visit(ast: AST) { ast.visit(this); }
 }