[Delivers #43535141] Populate help mappings and add any missing context help links

We've moved the context help configuration to become system AppConfig settings:

AppConfig[:help_enabled]         // defaults to false
AppConfig[:help_url]                 // defaults to "http://docs.archivesspace.org"
AppConfig[:help_topic_prefix]    // defaults to "/Default_CSH.htm#"

Context sensitive help is currently *disabled by default*.

This PR also includes the updated topic mappings (frontend/config/help.yml) and tooltips (frontend/config/locales/help/en.yml) based on the documented help from https://archivesspace.basecamphq.com/projects/10530659-end-user-documentation/posts/76785058.