Add admin creation routine

refs #7163
Ensure that a new admin account does not already exist

refs #7163
Relax schema check

Checking one table for its existence is more than enough. Creating a diff
implies conditional CREATE TABLE instructions and the like, what we want
to avoid.

refs #7163
Convert password salt to ASCII to avoid encoding issues with PostgreSQL
Query a particular login name and create database logins using the DbTool

refs #7163
Make it possible to skip the db-creation step

refs #7163
Do not show the db-creation step when the db-resource step was skipped

refs #7163
Improve the db-summary text and db-creation/-resource step handling

refs #7163