Refactored TrackLog CSV to TrackLog Object
And implemented loading/drawing TrackLogs
Also some NSAssert fixes in Survey+Mapping
Graphics layers are now static (and reused), so they must be cleaned
Moved Survey+mapping into survey to make instance variables real
Catch possible nil gps point
map layers will now be new for each survey
Fixed track log semantics - recording requires gps
temp workaround for 1to1 mapping of MP to GP, causing fail
In production, get all gps points with a unique time
In debugging (simulator points are identical), limit to a few seconds,  (get all real [moving] points)
Still crashing, comment out Assert temporarily
First, let the survey determine the semantics of Stop recording vs. stop observing
Second, do not start a new track log when stoping recording while observing.
Fixed UI glitch when stopping recording
Replace prior mission property with newer version if they have the same GPS point
Turn assert back on
Fixed errors in CSV format for tracklogs
remove aborted track logs, They should all be at least two points now.
Code to alert recovery from GPS failure
removed constraint on lat/long, since I could not guarantee that core location would comply
cleaned todos (issue #50) and removed dead code/comments