refactor: use consistent config file within DNAm QC pipeline

[sof202]

Description

This pull request will make it so that you no longer need to have your config file in a specific place for the QC to run. Every time the config file is sourced in the Rscripts for the DNAm QC pipeline, it uses the path assigned to the $RCONFIG variable that is set in the config file you pass into the main bash script (likely named config.txt).

This helps avoid user errors that stem from not knowing what the scripts actually want (like with #291).

Issue ticket number

This pull request is to address issue: #292.

Type of pull request

• Bug fix
• New feature/enhancement
• Code refactor
• Documentation update

Checklist

• I have performed a self-review of my own code
• I have commented my code, particularly in hard-to-understand areas
• I have tested my code to check that it is functional
• I have used linters to check for common sources of errors
• I have implemented fail safes in my code to account for edge cases
• I have made the corresponding changes to the documentation