Detect executables in Library addons for possible services

When scanning your addon libraries, if PERFLIGHT finds an EXE file, it should prompt the User if they want to add that as an Executable app in the Flight Services section. A recent example is that the FSS E-Jets 175/195 contains its own Navigraph installer inside of each aircraft folder.

D:\Games\MSFS\AEROSOFT\Community\fss-aircraft-e17x\navdata-updater.exe