Automatically impl deposit_event

[gavofyork]

The decl_module macro should automatically impl the deposit_event function. Right now it's manually implemented in each module which is boilerplatey.

[guanqun]

not all srml module implemented deposit_event, should we add a switch/flag in the decl_module to decide if we need to implement this function?

[gavofyork]

yup.

[gavofyork]

yes