Created new ScreenTools exported control for QML code to obtain screen DPI factor to be used for computing font point sizes. This code used to be in the tool bar code and now is available to all QML widgets.
Moved global mouse position tool into ScreenTools as I felt it would be a place to collect these sort of functionality.
Replaced Tree used in the Safety Component from a PNG file to a SVG file as the PNG was not scaling up properly.

Tool bar buttons now use QGCButton as base to inherit hover mode fix.
Made QGCButton.showHightLight into a public property so I could use it as a trigger for repainting the chevron button.

Reduced size of the main tool bar buttons accordingly.
Connect/Disconnect buttons (and link configuration combobox) now use the default height.

Button too small for when it switches to disconnect (multiple links adds a drop down icon to the button).

Although this should theoretically be a no-op it causes a crash in
Windows when running unit tests. Also parent toolbar in constructor.

Correct order of rotations to get roll, pitch and yaw corresponding to classical aeronautics convention and coherent with Fly view

Waiting for real fix to put back. Issue #1275

Fix for Issue #1255

Also fixed a typo (copy/paste error) in the TCP link settings loading where it was using the UDP port as the default value instead of the TCP port.

Switched to new. I’ve seen this before with other Qt classes and have
had to change the usage in the same way.

Removed "Clear Text" context menu from roll down dialog
Fixed "Clear Text" context menu in Info Dialog (renamed to "Clear Messages" in the process)

Shrunk the Message drop down dialog a bit.
Made the Message drop down dialog slightly transparent.

problem:
in src/ui$/HUD.cc copyImage(UASInterface* u): u->getImage() was called twice. The first called already erased the buffer.

changes:
src/ui/HUD.cc: copyImage(UASInterface* u): instead of getting the image a second time, we take the one we already fetched

I noticed that some times, the disconnect signal would get to the updateConnect button (tool bar) before the link was physically disconnected. That would cause it to count it as a still connected link and get the connect button logic out of sync.
While at it, added an interface to the UDP link to return its configuration instance. That allows the LinkManager to unlink it when disconnecting it.

The goal of this first installment is to organize the code a bit so it's more readable,
clean up a bit of left over cruft, and manage link configurations (and links in general).

- Much simpler UI
- MVC style qml programming model

Include support for both param sets

The parameters for calibration were changed in the latest master. QGC
needs to work with both. Hacked in for now, waiting on a true parameter
re-mapping implementation.

There's also a partial fix for the databits and stopbits. I'm unsure how to deal with the logic
around the 'is_cdc' variable, as I can't really follow what it's for.