DIH examples: Umbrella case for minimal examples

DIH examples were created long time ago by copy-pasting existing configurations and then adding DIH-specific configuration. Despite the goal being to explain how DIH configuration/settings work together, those settings are lost in the see of legacy and unused field types, solrconfig.xml defaults and support files.

This umbrella case and cases linked into it will focus on radically reducing configuration sizes and focus on demonstrating relevant feature most clearly.

The solrconfig.xml will feature disclaimer of not being production configured and will eliminate all defaults and non-critical definitions. The schema file will include only the fields and types relevant to the demo.

As DIH in the SolrCloud is a bit of a gray area and the examples are not using SolrCloud themselves, the version will also be skipped. Same with infoStream logging.