ACR-375 API review

ACR-375 API review
- add API description for doxigen
- divide repr to representation and state
- change return value from object to integer (error number)
- add keyword "void" for non-paremeter function
- remove a variadic function and make several functions
- change callback name from "fn" to "cb"
- move some define to be hide

Change-Id: I8d4374e3b7d50d7f218bd4f83790bf9b6a582ed8
Signed-off-by: Minchul Lee <slotus.lee@samsung.com>