Add a config action to modify an array of configuration

Problem/Motivation

We currently have the simpleConfigUpdate config action which works well for setting a single configuration value, but we have no way to interact with simple arrays other than completely overriding them.

Proposed resolution

Add a new config action, simpleConfigArray with 3 derivatives to append to, prepend to, and splice into an array. Append will be a wrapper around array_push(), prepend a wrapper around array_unshift(), and splice a wrapper around array_splice().