Bug 830644 - [Settings] Support High resolution devices

[rexboy7]

tidied up from Ismael's repo.

[basiclines]

Seem that apps/settings/style/images/radio_on.png assets are not anymore used in Settings app. Could we remove it?
It includes the off ones and their @2x versions.

[basiclines]

This deletions were cause because of an old merge, if the deleted lines are the newer ones we should kept it. (I'm talking only about the small lock icon not about all the rules using background-positions these are ok)
Review it with any Settings owner plx!

[rexboy7]

I've checked on the phone. Because in this patch the lock icon is put together with wifi signal sprites in one image, so I think this is no longer needed. I have checked it on the phone.. Will confirm with reviewer later if needed.

[rexboy7]

radio_on and radio_off are removed now.

[basiclines]

I've seen some issues in pairing window in settings:
Here is a patch for resolving it!

http://cl.ly/code/1A10291N2L3N

[rexboy7]

@basiclines Oh I didn't notice that. Thanks for the patch! I'm now updating css of wifi signal, will update the PR soon.

[rexboy7]

Updated by comments. Wifi signal and lock icon are now rendered separately, the same way as master branch.

@evelynhung May you review this PR? If you're busy on work week I can ask other owners. Thanks a lot!