Natively support Microsoft Flight Simulator 2020 (MSFS)

[ltoenning]

Internally, MSFS currently pretends to be FSX. However, in the future, MSFS should be supported natively to leverage new MSFS SimConnect features and to avoid user confusion.

Some work has already been done on the branches: feature/msfs_native_support, feature/msfs_native_support_rebase and feature/msfs_transponder

The following tasks must be addressed:

• Add separate MSFS plugin. This should use the MSFS-specific SimConnect API, for example, to read out the transponder mode. The method previously used to read out the transponder mode with FSX seems to be incompatible with MSFS.
• Add MSFS to swift itself (checkboxes, compile options, ...)
• Add MSFS to Datastore
• Update install & configuration instructions for MSFS