Feature Request: Support loading Cube schema files in Apache Ossie format instead of current YAML format

## Summary

Cube currently uses its own YAML schema format.

[Apache Ossie](https://github.com/apache/ossie) is an Apache-licensed open standard that defines a similar semantic model format — datasets with fields (dimensions + measures), relationships, primary keys, and more.

## Question

Does Cube plan to support loading schema definitions written in the Ossie format directly, instead of (or alongside) the current Cube-specific YAML format?

In practice, this would mean:
- Writing schema files in Ossie format instead of Cube's native `.yml` format
- Cube could parse Ossie YAML and use it to build the Cube model without any conversion step
- The same semantic model could be loaded by Cube without rewriting it in Cube-specific syntax

## Why this matters

- **Single source of truth**: Define the semantic model once, use it with Cube and other compatible tools
- **Vendor neutrality**: Ossie is open and Apache-licensed, not tied to any single vendor
- **Reduced duplication**: No need to maintain parallel schema definitions

The issue names no implementation files or tests. Start by locating Cube's current YAML schema loader and comparing its model with the Apache Ossie format; done means Ossie schema files load directly alongside or instead of Cube's native YAML without manual conversion.

Written by the indexing model from the issue text.