Support matrix parameters with no values mapped to boolean True when a method type is boolean or Boolean

It may be useful to support queries like "/products;inStockOnly", where a corresponding MatrixParam boolean method parameter will be set to 'true'. Path segments will return an empty value for such a parameter.

Effectively this JIRA is about affecting the mappings for MatrixParam parameters only. Unless it can introduce some ambiguities it can become a safe update.
#### Affected Versions
[2.0]

Use MatrixParam mapping as the entry point and search the repository for the implementation and tests covering matrix parameters, especially empty path-segment values. Confirm the existing behavior for boolean and Boolean parameters, then define tests showing that a valueless matrix parameter maps to true without changing other parameter mappings.

Written by the indexing model from the issue text.