Feature request: custom view logic support(extending default module/view logic)

This feature allows a developer to customize view logic in php file, instead of in custom operator, complicated template or custom datatype. This is a long idea I've thought about :).

It add a 'view logic' into override.ini so a developer can override template, also module logic. Currently it only support class_identifier and nodeid for 'view logic' condition.

I haven't found a better name for this feature. Welcome to comment and discuss :). 

I know in eZ 5 we have supported this, but because of infrastructure reason 4.x has still some time to go. (ref: https://confluence.ez.no/display/EZP/How+to+use+a+custom+controller+to+display+a+content+or+location)