Allow access to Map properties in expressions

Fixed parser eval and change detection.
Merge branch 'patch-0224-map-property-access' of https://github.com/chalin/angular.dart into patch-0224-map-property-access

Conflicts:
	lib/change_detection/dirty_checking_change_detector.dart
	lib/core/parser/utils.dart
	test/core/parser/parser_spec.dart
	test/core/scope_spec.dart