New VehicleLinkManager implementation

Updated mavlink forwarding implementation to forward all mavlink messages received on all channels onto a single UDP port. A new mavlink forwarding UDP link is created if forwarding is enabled. The mavlink settings page now has a Fact checkbox for enabling forwarding and a fact text field for specifying the host name.

Added mavlink forwarding as an option to UDP connections. Enabling this setting will cause every mavlink packet received by QGC to be forwarded on the link, with the exception of packets originating from said link.

qobject_cast is times faster dynamic_cast for objects that
inherit QObject. also, use auto keyword to not duplicate
class names.

New qml base log replay status bar

On desktop (Ethernet connection), the ground unit pushes UDP directly, which makes the use of an actual "Link" not possible. Instead, I've moved all of Taisync support to a "manager" owned by QGCToolbox.
Added a Taisync settings with some basics already wired and running.

- Pervasive change to automatically connect to known board types
- Lots of additional changes along with this:
- More exposure of objects/properties to Qml
- Much restructuring in LinkManager and LinkManager clients

- Pervasive change to automatically connect to known board types
- Lots of additional changes along with this:
- More exposure of objects/properties to Qml
- Much restructuring in LinkManager and LinkManager clients

- Pervasive change to automatically connect to known board types
- Lots of additional changes along with this:
- More exposure of objects/properties to Qml
- Much restructuring in LinkManager and LinkManager clients

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).