Update data access examples to use sqlclient

[rdruss]

This is a suggestion/question. Given the introduction of asynchronous data access through the sqlclient, should this be the recommended method for doing data access as documented in the java guide? @jponge, wdyt?

[jponge]

Absolutely, the whole guide needs to be revamped for v4 (e.g., no more Shiro authentication, move to SQL client, etc). And perhaps make the guide more concise.