Add flag to diable hrtf in webaudio

hrtf means "Head-related transfer function". It's to put
the source in a 3-D related position to the listener.

Without this feature, we can remove all the impluse wav
resources.
Add gyp flag use_minimum_resources and exclude unnecessary resources

Remove following resources:
1. Resources for media player control bar, this part is not usually
used, thus it could be overriden by web developers.
2. The ui resources are for aura/views, Android doesn't need it.
Merge pull request #222 from wang16/mini_pak

Remove some resources in pak file under gyp flag