Adding shell commands for modifying content.

1. Added methods to the ActivityManagerService remote interface
   that allow accessing content providers outside of an application.
   These methods are guarded by an internal signature protected
   permission which is given to the shell user. This enables a
   shell program to access content providers.

2. Implemented a shell command that takes as input as standart
   fagls with values and manipulates content via the content provider
   mechanism.

Change-Id: I2943f8b59fbab33eb623458fa01ea61a077b9845