Use user level installation rather than system level in advanced tutorial

[ncoghlan]

The new advanced tutorial uses system level installation for simplicity in:
​https://docs.djangoproject.com/en/dev/intro/reusable-apps/#using-your-own-package

This requires several of the steps to be run with administrator privileges.

It should be possible to avoid this (and make the section even simpler) just by changing the installation command in this section to:

python setup.py install --user

This obviously won't work in versions prior to 2.6, but there's no reason a beginner would be using such an old version (and if they are, lack of per-user package support is going to be the least of their problems)

Note that per-user installations can still affect the behaviour of system tools run as that user, so virtualenv is still the more robust solution. However, per-user installs also have a *lot* recommend them over system level installs (such as being usable on systems where you don't have admin access, not running downloaded code with admin privileges, as well as not affecting the behaviour seen by system services and other users of the machine).

[Carl Meyer]

Yes, this is a great idea. Python 2.6 is the minimum supported version for Django 1.5+ anyway, so that's not even an issue. Don't know why I didn't think of this option when reviewing that doc addition (well, actually, I do know why, it's because I don't have a use for --user personally), but it's totally the right thing here.

[Carl Meyer]

Patch looks good to me.

[Tim Graham <timograham@…>]

In dd0d2c0be56a28f868d501b06975984c138f4830:

Fixed #19216 - Switched to user level installation in apps tutorial.

Thanks Nick Coghlan for the suggestion.

[Tim Graham <timograham@…>]

In 958c1d12e584dfe493697edf1083f99b1a41d1a9:

[1.5.X] Fixed #19216 - Switched to user level installation in apps tutorial.

Thanks Nick Coghlan for the suggestion.

Backport of dd0d2c0be5 from master