Improve routed job environment configuration, simplify APEL configuration

New features include:

• Add non-OSG method for modifying the job environment (https://opensciencegrid.atlassian.net/browse/SOFTWARE-3871, #273)
• Simplify configuration of APEL scripts (#263)

Bug fixes include:

• Refine the APEL record filter to ignore jobs that have not yet started (#272)
• Add systemctl daemon-reload to packaging for initial installations (#274)
• Fix call to error() (#267)
• Improve robustness of BDII provider (#259)