Change the return value of the class_initialize method to int instead of bool

[gprossliner]

cobj itself has no dependency to the value of the class_initialize method. cobj just returns whatever is returned from the initialize_impl method. It's up to the caller to check it or not, or to assign any semantic with the value.

Why change to bool?

• the application could use it to return an error-code instead of just true or false
• we would not have an internal dependency to <stdbool.h>, which would effect all files getting in touch with cobj
• in v2 we will no longer need cobj.h, so there will be no need to include any (even standard) .h file