Update for getting service notifications.

- Fixed makefiles for IServiceManager.hal so that they can be
  automatically generated with hidl-gen.
- Added IServiceNotifications and
  IServiceManager::registerForNotifications
- Can now say IFoo::registerForNotifications("foo", <instance of
  IServiceNotification>)

Bug: 30804608
Test: hidl_test

Change-Id: I43829a323461e98cb70237b4e494abded59c173f
7 files changed