Metadata v 1.1

**This pull request is still in progress and should not yet be accepted.**

This pull request addresses the version 1.1 schema updates.  

It involves creation of the: 
- [x] [v1.1 /schema](https://github.com/project-open-data/project-open-data.github.io/blob/metadata-v-1.1/v1.1/schema.md)
- [x] [v1.1 example and template data.json files](https://github.com/project-open-data/project-open-data.github.io/tree/metadata-v-1.1/v1.1/examples)
- [ ] [v1.1 catalog and single_entry json schema files](https://github.com/project-open-data/project-open-data.github.io/tree/metadata-v-1.1/v1.1/schema/1_1_final) (#385)
- [x] [v1.1 /metadata-resources](https://github.com/project-open-data/project-open-data.github.io/blob/metadata-v-1.1/v1.1/metadata-resources.md)

As well as updates to: 
- [x] [/catalog](https://github.com/project-open-data/project-open-data.github.io/blob/metadata-v-1.1/catalog.md)
- [x] [/metadata-changelog](https://github.com/project-open-data/project-open-data.github.io/blob/metadata-v-1.1/metadata-changelog.md)