Please cherry-pick:

Please cherry-pick:
- introduced isSameCompanyNameAdded() which encapsulates checking for if a
  company name has already been used. This is, together with the thrown checked
  exception a last effort to prevent bad bad SqlException or any other
  "low-level" exception as they are more severage than this.
- thumb of a rule: always pre-validate if all conditions are met (return "okay")
  prior doing risky things where uncontrolled exceptions may be thrown.
- make company-owner (User), founder (Employee) and contact person (dito)
  managed before persisting the whole BasicData instance as this makes sure that
  no duplicates will end up in database

Signed-off-by: Roland Häder <roland@mxchange.org>