Docs: SQL store doc updates

Need to make several improvements to SQL store docs:

• Clarify the use cases for table and query stores
• If you want your SQL queries to update and delete entries, add the read-only="false" attribute or the .ignoreModifications(false) method to allow modifications to persistent storage. – Confusing and the wrong way around – re-word this to be something like "if you want the store to be read-only do ..." – the default is already false

Also provide more detail about using managed datasources in Server configuration. This is in the server guide only but should be included in docs for configuring persistence in caches.