Limit ObservationPointsOverlay drawing to 150 ms

Too many points, and the drawing can cause lag on slower devices.  This
will limit the impact.

Performance testing should be done to determine appropriate values for
the maximum duration, as well as how often to check the time.
Fix #766 - Don't check for app updates if Wi-Fi is disconnected and "Upload only on WiFi" setting is true
Alphabetize MainActivity.java imports
Clean up MainActivity.java whitespace
Merge pull request #837 from keverets/limit-history-drawing

Limit ObservationPointsOverlay drawing to 150 ms
Merge pull request #840 from cpeterso/cpeterso-issue-766-update-over-wifi

Don't check for app updates if Wi-Fi is disconnected and "Upload only on WiFi" setting is true