Changed method to property

Makes more sense as a property, the method may have implied that it
returned a copy of the array
We shouldn't really get an empty command text

So this saves having an empty version lying around in memory the whole
time
Missed TupleObjectInfo from diagram
Simplified MySqlDialect.PageQuery
Refactored the poco code out of ObjectInfo

Increases cohesion of the poco code and makes it easier to see what is
happening in the ObjectInfo static methods
Updated ndepend project