SWARM-1650: documentation of datasources should include validation settings (#685)
SWARM-1650: documentation of datasources should include validation settings (#685)

Motivation
----------
The `datasources` fraction documentation should include full examples
of datasource configuration as shown in EAP documentation:
https://access.redhat.com/documentation/en-us/red_hat_jboss_enterprise_application_platform/7.0/html/configuration_guide/datasource_management#example_datasource_configurations

This mainly includes connection validation settings, which is
important in case a DB temporarily goes away and then returns back.

Modifications
-------------
Added examples of MySQL, PostgreSQL and Oracle datasources, showing
all the configuration options included in the EAP documentation.

Result
------
More complete documentation for datasources.
nelsongraca/wildfly-swarm,nelsongraca/wildfly-swarm,kenfinnigan/wildfly-swarm,wildfly-swarm/wildfly-swarm-core,wildfly-swarm/wildfly-swarm,kenfinnigan/wildfly-swarm,kenfinnigan/wildfly-swarm,nelsongraca/wildfly-swarm,wildfly-swarm/wildfly-swarm,nelsongraca/wildfly-swarm,wildfly-swarm/wildfly-swarm-core,juangon/wildfly-swarm,wildfly-swarm/wildfly-swarm-core,kenfinnigan/wildfly-swarm,wildfly-swarm/wildfly-swarm-core,juangon/wildfly-swarm,wildfly-swarm/wildfly-swarm,wildfly-swarm/wildfly-swarm-core,wildfly-swarm/wildfly-swarm,juangon/wildfly-swarm,kenfinnigan/wildfly-swarm,nelsongraca/wildfly-swarm,wildfly-swarm/wildfly-swarm,juangon/wildfly-swarm,juangon/wildfly-swarm