Only show dialog to enable GPS on program launch

Show the dialog prompting to enable GPS when the program is launched. Do
not show it when returning back to the main screen.

This is a fix for issue #280.
Merge pull request #470 from aaronaxvig/master

Only show dialog to enable GPS on program launch (@aaronaxvig)
Refactored network communication code into a separate package.

* Minimizes code redundancies
* Detaches communication side from the app display side