General improvements to IdP installer

This PR has been tested

IdP: Updated latest chart values.yaml
Assisted installer: IdP values is stored in the working directory as values.txt
Assisted installer: Existing IdP values based on values.txt overrides default values set by the script as the suggested value
Assisted installer: Variable name changes for consistency
Assisted installer: Removed requirement for IdP backchannel cert and key
Assisted installer: Added option to use a custom namespace (instead of ORG_SHORTNAME)
Assisted installer: Added required variable ORG_PWD_RESET_URL
IdP: Updated documentation
Assisted installer: Rename installer script

sifulan-access-federation / ifirexman-training