Replace --once-remove-match with --once=unique

Fix possible escaping in names specified as options

Improve handling of templates

- Template mode: Use empty string if env var is empty
- Template mode: --search and --replace are optional
- Introduced better error handling with fatal errrors

Fix duplicate newline at end if using template

Update version

Update version to 0.3.1

Set version to 0.3.0

Fix version

Improve replace mechanism

- Replace --whole-line with --replace-line
- Fixed some bugs and issues
- Add --regex-backrefs

Improved search and replace

- Fix correct way of handling case insensitve non-regex search
- Added more verbose messages