[URL] Operations should be supported gracefully

[lewischeng-ms]

Currently, if we want to define a function or an action, we need to put two copies of definition in both domain class and controller class. The implementation in domain class is useless while only its declaration is used to generate the operation definition in the EDM model. The implementation in the controller class will get called actually. We should let user write only one copy of operation code and generate model according to that.

[lewischeng-ms]

Model building of functions and actions is supported.
Related commits:
1460432
b97531f

[chinadragon0515]

Support operation without additional controller is tracked with issue #378, and will be added in the release after 0.5 release.