[library] added DesignSpecActivity

[arok]

Added simple DesignSpecActivity

[lucasr]

Hmm, quite mixed about this one. I'd like to keep it simple. Providing a FrameLayout seems like the right level of convenience to debug existing code in any project. Activities tends to vary more from project to project and are harder to integrate if you have your own base Activity.

[arok]

I think just the opposite, if you have your own base activity use dspec are more simple. With base class you may setup individual build configuration for debug and using dspec.

[ataulm]

What if you have multiple libraries that require you to extend their Activity? This Activity could be an example for users that want to integrate dspec into their base :+1: but doesn't IMHO need to be part of the core library.

:+1: for keeping it simple.