Do not filter/hide line in linechartwidget when checkbox of the line is ...

differential pressure/airspeed calibration ui

override is not aviable in gcc 4.6 (only in 4.7).  Removed for compatability

Removed for compatability

LinechartWidget: fix removal of curves

A hefty commit to try to clean up MainWindow

flightgear hil: correct scaling of pressure for mavlink message and remo...

Filtering in plot perspective

Calibration fixes

flightgear hil: correct scaling of pressure for mavlink message and remove indicated airspeed from flightgear protocol, commit requires flightgear protocol update

This allows you to add XY graph plots of any data.  For example,
x,y position data of a servo.

There's no need to create multiple signals - connect() is fine with
connecting styleChanged(MainWindow::QGC_MAINWINDOW_STYLE)  to a slot
with no parameters.