Support shebang comments in copyright header validation

[nicu1989]

The copyright checker should support shebang (#!) lines in files and allow copyright headers to be placed after them, rather than requiring the copyright to be the very first content in the file.

Example: https://github.com/eclipse-score/persistency/blob/0abea3535a8fdc3e506a3d893fd2b89dbbb06b25/tools/qnx_credential_helper.py#L1

[nicu1989]

Automatically detect shebang lines and:

• accept copyright headers that appear immediately after a shebang line
• when using --fix automatically insert copyright headers after any detected shebang