Handle adjusting BasePath, utilizing discovered rootPath

[grayeul]

Description & Issue number it closes

Closes #6880 - to address deploying churchcrm in a subdir of webserver root.

Screenshots (if appropriate)

N/A

How to test the changes?

Deploy in a subdir, e.g. /var/www/html/churchcrm

Type of change

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to not work as expected)
• This change requires a documentation update

How Has This Been Tested?

Tested with a fresh git repository, and mapping src dir to /var/www/html/churchcrm. Verified that the initial setup of the ChurchCRM system proceeds correctly.

Checklist:

• My code follows the style guidelines of this project
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have made corresponding changes to the documentation
• My changes generate no new warnings
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published in downstream modules

[DAcodedBEAT]

(We need to consolidate the many routers at some point but) Great find!

I wonder if this is the issue many were facing when upgrading to newer versions of ChurchCRM (cc: @MrClever)