Add the serialization support for backend

Add the serialization support for backend

The Serializable class define the interface of serialize_to/deserialize_from
functions for internal binary and llvm binary. And also a print status
function for debugging.
The class which may need the serializaion support need to derive from it,
these classes including: Program, Kernel, ConstantSet, ImageSet and SamplerSet.
This patch just add serialize_to/deserialize_from internal binary support for
all these classes.

Signed-off-by: Junyan He <junyan.he@linux.intel.com>
Reviewed-by: Ruiling Song <ruiling.song@intel.com>
Reviewed-by: "Yang, Rong R" <rong.r.yang@intel.com>