Improved the setup of the shebang line of the startup script
Improved the setup of the shebang line of the startup script

Before this commit, the startup file for a Python app got the standard
shebang `#!/usr/bin/env python` which is suitable for many projects but
not for Python 2 or 3 only packages. Now the shebang of the project's
main script of read and copied into the startup script.

IngoHeimbach/shallow-appify