updates from SVN

 - OptAccessor's @errors was an Array, when it should have been a Hash.
 - Accessors may have among their @args other Accessors, which in turn may have their own errors. The nesting ones must notice that.
 - In validating the (should be) non-null sets, check for nil values.
 - Add the ability to check for validity in any type that response to include?, rather than just Array and Range
 - Add the ability to convert the args to a hash on-demand