Work out exceptions to CoDL double-space rules

[propensive]

We have a general rule that on a line, after two or more spaces, a single space does not constitute a new parameter. That is, two or more spaces are required to separate subsequent parameters. For key/value-style data, this works well most of the time, but not always. In a hypothetical project definition we could have, for example,

id           my-project
name         My project
description  The project I'm developing
keywords     experimental data cli

and experimental data cli would be treated as a single parameter, which would lead to a validation failure if keywords are not allowed to contain spaces, while it should really be three separate parameters (which would be interpreted as a repeated parameter according to the schema). But we would not want the description to be split on spaces.

Offering a way to specify (in a schema) whether a field can include spaces (or not) might help here. Concretely, this would mean that the example above could be correctly interpreted without additional spaces being required between the keywords.

[propensive]

Currently we use the following symbols in schemata:

• !: unique
• *: many
• +: at least one
• nothing: exactly one
• ?: maybe one

We could add another symbol to indicate whether parameters can contain spaces, but this would only be useful for + and *.