A minimalist `TextTemplate` engine is available for in-project use.
* supports only the bare minimum of features (no programming language)
* substitution of `${placeholder}` by key-name data access
* conditional section `${if key}...${end if}`
* iteration over a data sequence
* other then most solutions available as library,
this implementation does **not require** a specific data type,
nor does it invent a dynamic object system or JSON backend;
rather, a generic ''Data Source Adapter'' is used, which can
be specialised to access any kind of ''structured data''
* the following `DataSource` specialisations are provided
* `std::map<string,string>`
* Lumiera »External Tree Description« (based on `GenNode`)
* a string-based spec for testing
...turns out challenging, since our intention here
is borderline to the intended design of the Lumiera ETD.
It ''should work'' though, when combined with a Variant-visitor...
