Allowed `dotted name` nested var and store retrieval

[jkomoros]

Allow passing . in names to mean create and override sub-objects.

Do this for both var/let/let-multi and store/retrieve, as well as property

Note that this makes environment overlaying more complex and need a special helper.

Once this is done, perhaps have secrets be the place secrets are stored?

The simplest place to do this is property, where it doesn't even have to be that hard, and then it can be used for #45

• [x] Support dotted property names in property
• [ ] property should also have an else parameter
• [ ] Support dotted property names in let/let-multi
• [ ] Su[port dotted property names in store/retrieve
• [x] Support dotted names as template names
• [ ] Fix error introduced in f9f4023dfc2a0998b9dc3a9b17889225112bd3a4