console: shell: Support multiple modules

Ability to use Zephyr shell by multiple modules simultaneously, each
module for its own usage.

Old shell implementation enabled the user to call only one module
commands, not all of the modules simultaneously.

Change-Id: I0ef8fa2fd190b7490c44fe91d1016363258302c9
Signed-off-by: Yael Avramovich <yael.avramovich@intel.com>
Signed-off-by: Anas Nashif <anas.nashif@intel.com>