Add smart checks for Config and Schema API in Solr to avoid malicious updates

While working with Solr, schema and configuration changes without understanding can result in severe node failures, and much effort and time get consumed to fix such situations.

Few such problematic situations can be:

• Too many fields in the schema
• Too many commits: too short auto commit
• Spellchecker, suggester issues. Build suggester index on startup or on every commit causes memory pressure and latency issues
  • Schema mess-ups
• Text field commented out and Solr refuses to reload core
• Rename field type for unique key or version field
• Single-valued to multivalued and vice versa
• Switching between docvalues on/off
• Changing text to string type because user wanted to facet on a text field

The intention is to add a layer above Schema and Config API to have some checks and let the end user know the ramifications of the changes he/she intends to do.