Added Google Maps iOS SDK

Integrated the Google Maps SDK for iOS into the app.  Currently I've
got it replacing our old WebView by transitioning to a separate View
when the "Test Map" button is pressed.  Destination markers and path
generation is currently supported.  Next is attempting to replace our
current MapView with this new one.
Replaced Apple Maps with Google Maps

Removed the old MapKit code and replaced it with Google Maps SDK code.
Removed the second storyboard View and the transition between them,
instead the Google Maps map is now the MapView, and navigation
information is shown directly on the map.  Modified the path generation
code to zoom to the user's location when pathfinding begins.  Added
buttons for zooming to the user's location or to the middle of Midtown.
 If the user is in List View when they click these buttons, the map is
opened.  Added concentric circles for estimating walk distances.
Unfortunately, while I can supply titles to these circles, there's no
easy way to actually display the title on the map.  It would be
possible to use labels to accomplish this, but then they would need to
be dynamically sized/positioned when the map is zoomed/panned.  Seems
like a lot of work, might need to accept the circles without the labels
(will probably confuse people)  or just lose the circles.  We could
theoretically write the words using the Maps SDK by writing the
numbers/letters as polygons on the map (which would scale/pan) but this
seems like a lot of grueling hand-coding.  IDEA: Use markers with a
custom image (transparent-background text saying "10m Walk" and "5m
Walk") as markers placed at some point along these radii.
More bugfixes

Attempted to fix the duplicate entries bug.  I used a really
inefficient algorithm which runs in O(n-squared) time by checking every
destination we get back from the server against every aspect of every
destination we've already accepted and only accepts new entries which
differ in some capacity from existin entires.  I figure if two
destinations have the same name, category, lat, and long, they're
probably the same place (especially with double precision.)  Initial
tests were unable to get any duplicates to appear (while I WAS able to
immediately prior to this code change by simply starting the app,
closing it, and quickly starting it again.)  Also got rid of some
redundant re-allocation, instead just emptying the data structures.
Also tried to ensure that the path was updating when the user moved.
Tests seemed to indicate that this was working, but I don't have a real
device to test with in regards to accuracy, battery consumption, update
frequency, or server wait time.  Outstanding issues to be dealt with
include: Path should delete itself when you near your goal, Markers
shouldn't pop in if they aren't affected by the filter that's changing,
Still need to add labels to the concentric distance circles.
?

Changes that somehow weren't added in my last commit.