computing std dev in alascan

[VGPReys]

Checklist

• Tests added for the new code
• Documentation added for the code changes
• Modifications / enhancements are reflected on the haddock3 user-manual
• CHANGELOG.md is updated to incorporate new changes
• Does not break licensing
• Does not add any dependencies, if it does please add a thorough explanation

Summary of the Pull Request

This PR adds standard deviation computation when performing cluster analysis in the alascan module.

• The raw output file (scan_clt_*.tsv) now contain the standard deviation for all components of the score.
• The naming of the unclustered file is modified to scan_clt_unclustered (from scan_clt_-)
• Generated plots also contain the error bars

Related Issue

Closes #1332

Additional Info