Show download link to Piwik Mobile app when user is browsing with iOS/Android #2181

improve visibility of the Mobile App inside Piwik

If the piwik user is using a supported device (apple or android), then we can show in the Info box (blue) the message "Try Piwik Mobile App".
On hover it could say "You are accessing Piwik using Android phone... Have you tried the Piwik Mobile App?"

The link would be to Piwik Mobile app page, or maybe we can directly link to the download pages themselves:

• Android: market://details?id=org.piwik.mobile
• iOS: http://itunes.apple.com/us/app/piwikmobile/id385536442

This would always be displayed, unless there is an update available and then the box will be orange as normal.

Relatively easy to do, and would increase Piwik Mobile App which is good

(In [4831]) Fixes #2181 - show "Piwik Mobile" link in the top bar, if user is using android/iphone/ipod/ipad