Resolve #21 - add extension method to ICollection<T> that replaces the contents

This would be used when you cannot assign directly to the collection (say it was
a read only property, or there is another reason why the same instance must be
used).  It clears the collection and replaces all of its elements from a
replacement collection.
Resolve #11 - add shortcut extension method to IDbCommand to add a parameter

This is really just a convenience method to add a named parameter in one line
rather than needng four lines of code to do the same.  Nothing fancy.