ParameterCollectionHashLookupParameterRenameBug()

Add test to demonstrate the parameter rename bug that exists with the new hash-based parameter lookup.
NpgsqlParameter[Collection]

Make parameters aware of their owning collection.
Enforce a parameter can belong to any collection only once.
On paremeter name change, invalidate owning collections's hash lookups.
When a parameter's collection changes, also make sure it is marked as unbound.
Add function to remove a parameter by name.
Merge pull request #136 from glenebob/param_name_change_bug

Param name change bug