Datasources subsystem - small user experience enhancements

This jira contains some small typo findings and suggestions for user experience enhancements when working with the datasources subsystem:

1, Schema file contains a typo on line 1037: "Thios tag is not used ..." -> "This tag is not used ...".
2, Description for flush-strategy attribute on both data-source and xa-data-source says there are only three valid values, when in fact there are ten. When setting the attribute value to something invalid, the error message correctly lists all ten, except UNKNOWN is listed as null.
3, Description of pool-fair attribute on both data-source and xa-data-source has, IMHO, weird word order: "Defines if pool should use be fair" -> "Defines if pool use should be fair".
4, Although the description of the attribute transaction-isolation lists valid values for the attribute, there is no validation. It is possible to assign any value to the attribute. Could the validation be added in a similar manner like it exists for flush-strategy attribute? This is the case for the attribute on both data-source and xa-data-source.
5, The description of background-validation attribute on data-source and xa-data-source says server needs restart when the attribute value is changed on an enabled data source. However, it's restart-required value is no-services and the CLI does not warn the user that server needs to be restarted once the background-validation value is actually changed.