Refactor helper::script to not use exec function

- Do not file resources for /tmp script files
- Create dir, file, chmod and exec within command
- Allow usage of exec-like unless
Remove exec function
Remove exec usages
Do not set default unless
Run script directly not using `/bin/bash -ec`
Remove $scriptFilename
Merge pull request #39 from tomaszdurka/issue-39

Refactor helper script to not use exec command