MdeModulePkg: Add sample help information for HelloWorld application.

Since Shell supports finding help information from resource section
of application image. We enhance the HelloWorld to add help information
string. After the HelloWorld are loaded in system the help string will
be stored in resource section of the application image.

Cc: Feng Tian <feng.tian@intel.com>
Cc: Jaben Carsey <jaben.carsey@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Cc: Ruiyu Ni <ruiyu.ni@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Qiu Shumin <shumin.qiu@intel.com>
Reviewed-by: Ruiyu Ni <ruiyu.ni@intel.com>
Reviewed-by: Liming Gao <liming.gao@intel.com>