Removed completely unused variables. Ifdef’ed out variable which is
referenced from commented out code.

Fixes Issue #542

This patch fixes a bug that display 0 for distances to waypoint more
than 10km.

Besides that, it also homogenize the naming of the label to
"distToWaypoint" instead of "distToWP". Old configuration files (in
home directory), should be hacked or removed in order to see this
change.
Signed-off-by: Paul Chavent <paul.chavent@onera.fr>

Also commented out noisy serial link error output

MainWindow::loadDataView has been commented out for 9 months now.
Removed commented out code instead of leaving cruft in.

showLabel was connected to signal but not set as a slot

There is no such things as a clicked signal on QWidget. You activate
new UAS from right-click menu.

ui->waitingLabel is deleted and set to NULL when mode is PX4. Must
check for NULL before using it.

The connect call was generating debug output to identify that it was
failing. After looking at the code realized that this connect is not
needed. The group box is removed when UASListWidget::removeUAS method
is called.

Second change in the file fixes a crashing bug when the last UAS is
removed. Need to exit the iterator after we modify it.

Right-click menu works cleaner.
Coloring of output text is correct.
Output text now handles all severities of messages.

All it does is clutter the terminal and it's not doing anything anyways.