Drop unused #include <QPushButton>

Signed-off-by: Stefan Hajnoczi <stefanha@gmail.com>
Change "Xmit" to "Send"

"Xmit" is not obvious to users.  Hopefully "Send" is more self-evident.

Signed-off-by: Stefan Hajnoczi <stefanha@gmail.com>
Add tooltips for status bar widgets

Signed-off-by: Stefan Hajnoczi <stefanha@gmail.com>
Make xmit and metronome button state persistent

It's handy to save the xmit and metronome enabled/disabled state between
executions.  That way users need to click less if they restart the
client.

Signed-off-by: Stefan Hajnoczi <stefanha@gmail.com>
Explain that "Audio system" is for troubleshooting

We automatically select the preferred audio system.  Normally it is not
necessary to switch audio systems.  Make this clear in the audio
configuration dialog by moving the audio system dropdown to the bottom
and adding text explaining its purpose.

Signed-off-by: Stefan Hajnoczi <stefanha@gmail.com>
Add software monitoring settings to audio configuration dialog

The ChannelTree widget currently displays local channels and their
mute/unmute checkbox.  In practice this only needs to be configured
once, depending on whether software or hardware monitoring is used.

The local channel mute is easily confused with the send (aka xmit)
feature.  Both are a type of "mute" but they have different behaviors.
We will remove local channels from the ChannelTree widget soon, so move
the software/hardware monitoring option into the audio configuration
dialog.

Signed-off-by: Stefan Hajnoczi <stefanha@gmail.com>
Apply new software monitoring setting

Signed-off-by: Stefan Hajnoczi <stefanha@gmail.com>
Stop handling ChannelTree local channel mute in MainWindow

The software monitoring setting now lives in the audio configuration
dialog.  Stop handling ChannelTree local channel mute signals in
MainWindow.

Signed-off-by: Stefan Hajnoczi <stefanha@gmail.com>
Drop local channels from ChannelTree widget

Software monitoring is now a audio configuration dialog setting.  Stop
displaying local channels and their mute buttons in the ChannelTree
widget.

A nice side-effect is that the ChannelTree code is simplified
significantly.

Signed-off-by: Stefan Hajnoczi <stefanha@gmail.com>