Add Mobile specific Semantic conventions

[bryce-b]

What are you trying to achieve?

I'd like to define mobile device/application specific semantic conventions.

Additional context.
The current semantic conventions are mostly container/service centric.
Mobile applications are an important part of the software stack, and need to be monitored just like any other link in the chain. There should be some predefined conventions around mobile specific platform details in the resource spec.

Ideally the following should be added:

• device.id : a unique identifier for the device (e.g.: vendor identifier for iOS)
• device.model : model of the device (.e.g iPhone3,4)

It would also be useful to have a parsable os.version