Prevent schedule update with invalid action

Actions are now defined in the config. I have modified the sample config file to show the change. Renamed "action_overrides" to "valid_actions" since we are now piggy-backing on the same config value to do action validation. Valid actions need a [action_<name>] section in the config file, otherwise the default values are provided. Any additional params that are extended from the base config values are defined on their own. Most of the test files were modified, just to inject these new config values for testing purposes, the only significant changes are in tests/unit/v1/test_schedules.py

Fixes rm883