Fixes error when creating the db for Query Execution perf tests.

Fix for #994.

This makes the process a bit slower since it calls SaveChanges more often, but it works well.

Additionally fixing kproj and project.json files for the perf tests to reflect they are console apps and not libraries.

@lukewaters 
I originally had the () and I think they were removed in @AndriySvyryd 's code cleanup a little while ago.  is it best form to have the parentheses or not?