FlightGear - Flight Simulator FGAddon

* Models/Interior/Panel/Instruments/{KT76A,chrono}: delete.
* Models/Interior/Panel/Instruments/ki206: copy from the DR400-dauphin. Modify to use nav2
instead of nav1. (Note: this is because the stock KI206 in $FG_DATA/Aircraft/Instruments-3d
is not satisfactory).
* Models/Interior/Panel/panel.xml: use the stock M877 clock and place it like on [1].
Swap the positions of COM1/NAV1 (now on top) and COM2/NAV2 (now on the bottom) in the radio stack.
Use the stock KT76A from $FG_DATA/Aircraft/Instruments-3d.
Add a KI206 instrument for NAV2, where the (oversized) clock was previously, like on [1].
* pc12-base.xml: load the nasal module for the M877 clock.

[1] http://cbaviation.com/wp-content/uploads/2017/06/Cockpit-3.jpg