BUG #13743: Incorrect default value in documentation for --serviceaccount option to Postgres installer

The following bug has been logged on the website:

Bug reference: 13743
Logged by: Christopher Kline
Email address: ckline(at)onezero(dot)com
PostgreSQL version: 9.4.5
Operating system: Windows 10
Description:

If you run the postgres 9.4.5.1 installer with the "--help" option, it
contains this in the output

--serviceaccount <serviceaccount> Sets the operating system user account
that owns the server process. Defaults to 'postgres'.
Default:

--servicepassword <servicepassword> Sets the password for the operating
system user account that owns server process. Defaults to superuser
password.
Default:

This is actually incorrect, as it does not use 'postgres' and the superuser
password if you omit these parameters. Instead it installs using "NT
AUTHORITY\NetworkService" as the service account, and nothing for the
password.

These are the correct values for default installation -- it's just the
documentation in the output of the "--help" option that is incorrect.