LinkAhead renaming: Allow but deprecate old CAOSDB_CONFIG_ environment variables.
From README_SETUP.md:
All configuration environment variables should be change from
CAOSDB_CONFIG_...toLINKAHEAD_CONFIG_.... The old environment variables will remain deprecated but valid for some time, but mixing old and new variables is forbidden: If you rename one, you have to rename all.
- Deprecation and consistency check (either CAOSDB or LINKAHEAD, not both) is implemented.
- Followup issues created if necessary