bump for update

start from 4.20 for automatic builds

bump for 4.22

fixed 4.18

Update UnrealEnginePython.uplugin

fixed 4.21 build

auto-copy scripts to packaged

- copies content/scripts in plugin and project
- copies embedded python if used

Update README.md

ported to 4.15

fixed autodetection for PyFbxFactory 20tab#488