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
https://github.com/angular/angular/commit/a43ed79ee7d49ec55a0adea9b587ed67780c870c. 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); }
 }