Combined pulls #1113 and #1115

Plus a large number of other changes to allow for orderly shutdown of
objects without crashes or asserts. This is need for unit tests to
create/delete global state around every test.

New Singleton Manager

Support enabling fatal warnings via user_config.pri file

Restructure LinkManager/MAVLinkProtocol

Give user choice to disconnect all links on MainWindow close

Needs to be re-written

Put audio output into a worker thread.

Bump Linux Qt requirement to 5.3 in README

Remove unnecessary QGCStatusBar

Uninstall is in Add/Remove Programs

Verify that protocol files are not out of date

Separate install of SDL on OS X not needed

Delete any temp log file before each unit test case

New FactSystem

Allows parameter access from QML among other things

This reverts commit 4d033715.