Allow files as input

[NikitaKozlov]

To ease testing and maybe a potential possibility to generate multiple projects at once we can add an option to pass a path to a script as input.

Possible behavior:
main() method excepts a path as a string. Then we have three potential cases:

• input is a path to a file - read file and use its' content as input
• input is a path to a directory - consider each file inside as a separate input
• else show UI