Change ContainerExecutor's primary lifecycle methods to use a more extensible mechanism for passing information.

As per description in parent JIRA : Adding additional arguments to key ContainerExecutor methods ( e.g startLocalizer or launchContainer ) would break the existing ContainerExecutor interface and would require changes to all executor implementations in YARN. In order to make this interface less brittle in the future, it would make sense to encapsulate arguments in some kind of a ‘context’ object which could be modified/extended without breaking the ContainerExecutor interface in the future.