Fix up alias query/plugin config

[ryanrdoherty]

Multiple issues found that can be fixed together:

1. 1 primary key def can be made in XML (last one selected); add include/exclude logic and throw error if 0 or >1 remains

2. If query and plugin are both null, we will always throw NotFound for all IDs of the recordclass; this should not be possible, so error on model parse if both are null (maybe change RNG to require one)
3. To make logic more clear, if query is selected, wrap in a plugin and then always just user plugin logic