When Evolver sets itself up, it looks for the presence of a Version

table, falling back on bootstrapping if it doesn't exist. This was done

by attempting a direct query and then initiating bootstrap if no

Version items were present or if the table itself didn't exist in the

database.
Handling this by watching for an error isn't ideal, and can impact any

parent transaction, or obscure other issues. Instead, the better

approach is to look to see if the table exists in the database directly.
This change implements that, and takes care of a similar type of check

in one of the Evolver unit tests.

Unit tests pass for all databases.