Fix/remove unwrap

[MartinKl]

more robust code

more warnings

file name determination in exmaralda export is now configurable

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 67.56152% with 145 lines in your changes missing coverage. Please review.

Project coverage is 81.36%. Comparing base (d41ea30) to head (2094e45).

Files	Patch %	Lines
src/manipulator/re.rs	62.13%	18 Missing and 21 partials :warning:
src/manipulator/collapse.rs	63.07%	15 Missing and 9 partials :warning:
src/exporter/exmaralda.rs	77.22%	14 Missing and 9 partials :warning:
src/importer/exmaralda/mod.rs	80.00%	9 Missing and 4 partials :warning:
src/importer/file_nodes.rs	69.44%	7 Missing and 4 partials :warning:
src/manipulator/check.rs	61.90%	7 Missing and 1 partial :warning:
src/manipulator/link.rs	38.46%	5 Missing and 3 partials :warning:
src/importer/toolbox.rs	65.00%	6 Missing and 1 partial :warning:
src/exporter/sequence.rs	25.00%	5 Missing and 1 partial :warning:
src/importer/meta.rs	57.14%	3 Missing :warning:
... and 1 more

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #262 +/- ## ========================================== - Coverage 81.73% 81.36% -0.38% ========================================== Files 41 41 Lines 15349 15453 +104 Branches 15349 15453 +104 ========================================== + Hits 12546 12573 +27 - Misses 1063 1139 +76 - Partials 1740 1741 +1 ```

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