Prevent Non-Rendering Where Clauses by Default

[jeffgbutler]

Potentially Breaking Change

Most of the conditions in a where clause support optionality - meaning they may or may not render based on their values at runtime. If all conditions drop out of a where clause, then the entire where clause may be dropped from rendered SQL. This presents a danger in that a statement may inadvertently impact all rows in a table (for example, all rows could be deleted).

Out of an abundance of caution, this PR changes the default behavior pf the library. If a where clause is coded in a statement, but the where clause doesn't render, the library will now throw a NonRenderingWhereClauseException. This default behavior can be overridden globally, or on each individual statement.

If this new behavior is acceptable, then no code changes are required. If you would like to allow a statement to be rendered even if the where clause will be dropped, then you must either change the global configuration of the library, or change the configuration of the statement through the DSL. Configuration options are documented on the "Configuration of the Library" page.

This is related to #509

[coveralls]

Coverage remained the same at 100.0% when pulling 21e45e7 on jeffgbutler:statement-configuration into 1a51903 on mybatis:master.