Small DICOM Export / Import fixes

[wahln]

This pull request fixes #797 and #798 in matRad's DICOM importer and exporter functionalities. The most important changes involve adding support for new dose types and comments, updating patient data handling, and ensuring compliance with DICOM standards.

DICOM Exporter Improvements:

• Added support for new dose types such as LET, BED, alpha, beta, effect, and RBE in matRad_exportDicomRTDoses.m. This includes setting doseUnits to RELATIVE when appropriate. [1] [2]
• Ensured ReferencedRTPlanSequence is set as it is a conditionally required field according to the DICOM standard.

DICOM Importer Enhancements:

• Updated matRad_DicomImporter to handle multiple patients and selected patients. This includes changes to the patients and selectedPatient properties and their usage in various methods. [1] [2] [3] [4]
• Added handling for DoseComment in matRad_importDicomRTDose.m to map dose comments to dose types.

Fixes #797, #798

[codecov]

Codecov Report

Attention: Patch coverage is 38.88889% with 22 lines in your changes missing coverage. Please review.

Project coverage is 51.28%. Comparing base (2f04478) to head (44dd21e).
Report is 1 commits behind head on dev.

✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
...m/@matRad_DicomImporter/matRad_importDicomRTDose.m	0.00%	9 Missing ⚠️
matRad/gui/widgets/matRad_importDicomWidget.m	0.00%	9 Missing ⚠️
.../@matRad_DicomExporter/matRad_exportDicomRTDoses.m	85.71%	2 Missing ⚠️
...@matRad_DicomImporter/matRad_interpDicomDoseCube.m	0.00%	2 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##              dev     #799      +/-   ##
==========================================
+ Coverage   51.25%   51.28%   +0.02%     
==========================================
  Files         598      598              
  Lines       37272    37300      +28     
==========================================
+ Hits        19104    19128      +24     
- Misses      18168    18172       +4     

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[github-actions]

Package	Line Rate	Health
coverage Package 1	51%	➖
Summary	51% (9557 / 18650)	➖

[github-actions]

Test Results

  3 files  ±0    3 suites  ±0   33m 44s ⏱️ -14s
274 tests ±0  274 ✅ ±0  0 💤 ±0  0 ❌ ±0 
918 runs  ±0  913 ✅ ±0  5 💤 ±0  0 ❌ ±0 

Results for commit 44dd21e. ± Comparison against base commit 2f04478.

♻️ This comment has been updated with latest results.