Make minor changes for current versions of PHP

[halfer]

The tutorial is perfectly OK to use now (with PHP7) but there are a few simplifications I can make:

• Chapter 1 makes a reference to using libraries for the password_compat, which was used for versions of PHP prior to 5.5. These versions are out of support now, so this can be removed.
• Remove vendor/password_compat/lib/password.php from Chapter 6
• Give the whole tutorial a read-through to ensure there are no remaining references to using libraries.

This will need a new text version (v4) and code changes can merge into latest branch (rebase5).

[halfer]

Remove the password.php in separate rebases in:

• Installer (done)
• Login screen (done)

Additional issue:

• Generating the latest version (v4) has a problem because it forces the existence of vendor/password_compat - I think in doSubmodulesManually I need to look in the .gitmodules file and see what things to add to the diffs (done).

[halfer]

This just needs to be deployed.