Make result methods templates of their statement, not their statement's policies
Added first draft of custom query
Added first test
First custom query sent to MockDb
Can compile (very simple) custom queries and selects
All tests compile again...
Added missing file
Added run and prepare to noop, allowing void custom queries
Fixed parameter determination and added execution of void statements
Added prepared_execute to MockDb
Added free function where()
Added into() free function
Added method to set return type of custom query
Merge branch 'feature/custom_query' into develop