Code Cleanup. Only functional change is the added permissions on the broadcasts.

* Removed unused ScannerService.

* Refactored the use of generic intent messaging to specific message
* actions, namespaced to their sending class.
Cleanup naming conventions for Intent arguments. Added consistency to
using string constants for Intent arguments, rather than mixing strings
and string constants in the same block of code.

* Renamed messages to be clearer about their actions, based on what I
* can see the code is doing, specifically MainActivity
* ACTION_UNPAUSE_SCANNING and ACTION_UPDATE_UI. That is the only roles I
* could find for these actions, and created these names accordingly.
* (will address the FIXMEs in later checkin)

* Added permissions restrictions to the message broadcasts for Cell,
* GPS, and WIFI. If the receiver does not have the respective
* permission, they cannot receive the message. I just realized while
* typing this, I need to see if permissions are required on the
* reporting broadcasts.
Merge branch 'cleanup' of https://github.com/garvankeeley/MozStumbler into cleanup