bug 47671 -- don't show crashy photo button if no camera present

We were crashing when trying to take a photo if no camera was
present on the device, since no activity can be found for the
camera intent and an exception is thrown.

Work around this by simply checking if the device has a camera
via the package manager feature checks, and hiding the menu item
if relevant.

GitHub: https://github.com/wikimedia/apps-android-commons/pull/13
Change-Id: I635946ed32cf768917db4a8dff0058061e45e6ec