Subclass of QMessageBox which re-implements the static public
functions. There are two reasons for this:
1) The QMessageBox implementation on OSX does now show the title
string. This leads to message boxes which don't make much sense. So on
OSX we set title to text and text to informative text.
2) If parent is NULL, we set parent to MainWindow::instance. This
prevents message boxes which can go behind MainWindow

Path through code allowed for xmlfile to be used when file was not
opened. Also changed qWarning->qDebug to allow QT_FAIL_WARNINGS to be
used to find bugs.

Also fixed some code in QGCPX4VehicleConfig to remove unnecessary DialogBare references.

Now properly checks for if QUpgrade submodule has been cloned.
Allows for disabled QUpgrade compilation.
Altered some code so that compiling without the QUpgrade module could
succeed.
Updated README about QUpgrade submodule.

PX4 config: Remove the specialized throttle handling - this needs testing, but doing the math on paper it doesn’t look like a special case is needed / wanted here.

Use the reversed values for the four control channels as well. Not using them would make the display very confusing.

Enable RC calibration mode during RC calibration to tell vehicle to ignore stick inputs for that period

This fixes a bunch of bugs with setting the title for widgets, deleting
widgets, etc.  It also reduces the amount of code duplication, which is
always a good thing.

- MAV resets the RC_DSM_BIND param back to 0 automatically but QGC
doesn't know about this and thinks the parameter hasn't changed when the
pair button is hit a second time. Since it thinks the param has not
change, it doesn't transmit the update.
- This implements method to allow to optionally force QGC to send the
update. By default it does not
- Also added copy statements to include the two missing DLLs
(QtDeclarative and QtScript) automatically as part of Windows build.