Add auditing to server CLI.
Also:
- simplify auditing in API layer
- reduce number of AddMeta calls
- have models serialize themselves
- more consistent field naming
* New auditing API outputting to syslog via TLS
* New config section for specifying remote syslog server IP, port, and cert.
* Legacy audit API retained for access history feature
* Consistent license message for all the go files
* Fixing the last set of unconsistencies with the license headers
* Addressing PR review comments
* Fixing busy.go and busy_test.go license header
* tweak utils.Merge docs
* move merge_test to utils_test package for easier testing
* utils: support MergeConfig and StructFieldFilter
* constrain updating certain fields by the restricted system admin
* api4: break out license and config from system
* app: move some config functions from admin.go to config.go
* add ExperimentalSettings.RestrictSystemAdmin
* forbid various actions to restricted system admin
* update default.json
* fix function names in errors