Create User table and concept of admin users

We might borrow the idea from Jenkins. If there is no user yet, display a hash in the console. User can authenticate using username admin and that hash.

This sub task should only focus on admin user creation (via REST endpoint for now) and database table creation. It should have role based ACL setup.

Implementation detail:
when MT starts, it will print an initial password to the log console and write to a file $HOME/initialPassword.

REST endpoint to create accounts

Once an account is created, the initial password is no longer valid.

Another REST endpoint to query all accounts (admin only)