NFC sharing for Course and Profile Fragments

Note: Currently we share whatever is on the screen, be it a friend’s
Profile or yours. The alternative is to always share the logged-in
user’s profile if they are on any Profile screen.

Also, we’re currently using intent filters to handle NFC intents so
that we can trigger our choice of Activity (MainFlowActivity) rather
than the application default (LoginActivity). I mention this because
someone who touches this NFC code in the future may be inclined to use
Android Application Record (AAR) in the NFC push messages
(NDefMessage). This is not what we want, at least in it’s current
implementation (API 18) because “AARs are only supported at the
application level, because of the package name constraint, and not at
the Activity level as with intent filtering.” (quoted from
http://developer.android.com/guide/topics/connectivity/nfc/nfc.html#aar)
. In other words, specifying AAR means opening the LoginActivity when
we receive a Flow NFC event.
Remove unnecessary argument checking in ProfileFragment