We should have ports concept in the Modules

[mraduldubey]

As we use the fw to build applications, it is quickly apparent that single instance of a module can be reused to support multiple features.
Consider a case of mp4writer instance, this can be used to support continuous write, export etc.
The input to the module may differ in each of the feature. That is, the image frames given to the mp4 writer will come different sources in such cases.

The problem is that to support this, we need to take two image input pins, which does not make sense because, only one of the frames will be written at a time.

Currently, this is achieved by using relay to off and on the pins, adding multiple input pins to the module and hacking the input pin validation and the meaning of input pins change.

Following may be the alternative way to achieve this in framework:

1. Instead of adding pins directly to the module, we can connect pins of same "intent" to a common port.
2. The port is connected to the module
3. The port implements strategies to select which input pin to consider at a given time. Enabled relay can be one such strategy. Priority can be another.