Frontend CRUD enhancements (character/account creation and management)

[strikaco]

Brief overview of PR changes/additions

• Updates Bootstrap to v4 stable (the beta in use had some irritating bugs that have since been resolved)
• Enables the use of Django Messages framework
• Adds a web-based account registration form
• Adds links to reset password / create new account on login pane (resets require SMTP configuration to actually work, but the functionality was already enabled by account of django.contrib.auth.urls-- I just made it prettier). Uses Django's password reset workflow.
• Modifies the series of password reset forms to use Evennia's CSS instead of Django admin's.
• Adds a dropdown for authenticated users allowing them to change their password.
• Prettifies the "change password" form to use Evennia's CSS instead of Django admin's.
• Adds placeholders to dropdown menu for players to quickpuppet/manage characters on the website.
• Fixes a bug on the login pane where error messages weren't being displayed (was calling form.has_errors instead of just checking form.errors)
• Web-based chargen based on predefined form
• Character puppeting within the context of the website

Other info (issues closed, discussion etc)

Another notch towards #533

[aliceafterall]

I meant to update to the latest stable! It's a good idea to ensure nothing broke due to this update, so I'll test that out ASAP.

[strikaco]

Currently, domain is set to "example.com" per the default configuration of what appears to be the Django Sites framework. This should probably be resolved during evennia --init but is beyond me to fix-- it also impacts the reverse "view on site" link in the Django admin (if get_absolute_url is implemented on the object in question).

[Griatch]

Overall, some very good improvements here. The style changes and more elaborate input for registering looks nice and professional! Interesting to offer a default example of online character-creation - I like it, but have given some comments so as to make it clear this is just that - an example (the more advanced and game-specific code rather belongs in a contrib or a wiki tutorial).

(Should also point out that I was looking through #533 and I think this may lay the groundwork but otherwise goes a little outside the frame of what that issue covers - this allows for account/character creation for the users themselves; #533 is more humble in that it aims to clean up and make the web-Admin more usable for creating Accounts and linking them to Characters/Attributes from the perspective of a staffer).

[Griatch]

@strikaco Is this ready for re-review?

[strikaco]

No, not ready yet; the dropdown bug is still outstanding.

[strikaco]

Fixed the dropdown bug but still have some tidying up to do. Further updates as events warrant...

[strikaco]

So we now have a form-based character creation page, a character update page, a character management page, a character deletion page, ownership and lock checks for both, character puppeting on the website, a password change workflow, and unit tests for all website views. Everything works as far as I've thought to test it.

I think that's enough changes for one PR... for all this entailed, I'm missing out on a lot of Hacktoberfest cred :\

@Griatch ready for you to tell me how much my documentation sucks :)

[Griatch]

The documentation of some of these functions is too sparse 😛 But this is great work, I think it's worth merging and resolve any remaining issues as they come along. Thanks for your hard work!