Merge pull request #1108 from DonLakeFlyer/Singletons

src/AutoPilotPlugins/AutoPilotPluginManager.cc

src/AutoPilotPlugins/AutoPilotPluginManager.h

src/AutoPilotPlugins/PX4/Tests/FlightModeConfigTest.cc

src/FactSystem/FactSystem.cc

src/FactSystem/FactSystem.h

src/QGCApplication.cc

src/QGCApplication.h

src/QGCSingleton.cc

src/QGCSingleton.h

src/comm/LinkManager.cc

src/comm/LinkManager.h

src/qgcunittest/LinkManagerTest.cc

src/qgcunittest/LinkManagerTest.h

src/qgcunittest/MavlinkLogTest.cc

src/qgcunittest/MockUASManager.cc

src/qgcunittest/PX4RCCalibrationTest.cc

src/qgcunittest/QGCUASFileManagerTest.cc

src/qgcunittest/TCPLinkTest.cc

src/qgcunittest/UASUnitTest.cc

src/qgcunittest/UnitTest.cc