Use INSTALLED_APPS to look for unicorn components by default

[adamghill]

PR for #210.

• Use INSTALLED_APPS for components by default
• Cache the component look-up since they shouldn't move after they are found
• Test that templates work correctly (or just default to unicorn as the sub-folder)
• Update startunicorn to accept application name (should this default to "unicorn" if it's missing? or should it be required?)
• Update documentation for creating new components, breaking changes, etc

[nerdoc]

regarding the application name: I'd recommend keeping it as simple as possible. Keeping unicorn components in a separate app doesn't scale and adds more complexity. IF anyone wants to do that, nobody prevents him from doing so: create an empty app, create unicorn components in it and done. If you force the user (who doesn't want tnat) to create a unicorn app, or any "named" unicorn app, it's not a help, but a burden. So why not remove the setting completely? Alternatively, as help for beginners, make it mandatory for the startunicorn command: The dev has to name an app where the initial/example templates are placed in. You have to place them anywhere, so why not choose an app. Forcing him (or even encouraging him) to use a "unicorn" named app just adds unneeded complexity IMHO.

[nerdoc]

Oh, and keeping the unicorn components in a "unicorn" template subfolder is good IMHO. Others (reactor: unmaintained, etc.) do that too. Just keep in mind that, in a bigger project, it can get problematic, if two apps use a "counter" component. While normally they could be distinguished by foo/counter.html and bar/counter.html, in unicorn both would be named unicorn/counter.html. This could be solved in larges scaled projects by using unicorn/foo/counter.html - BUT: this adds complexity as well. you have to maintain an <app>/<component>.html structure beneath your templates/unicorn folder again. One solution would be to not look in templates folder, but create a separate structure as sibling to it: either "unicorn", or "components", as other projects do. Then you keep the components separate from normal templates in the first place.

[adamghill]

@nerdoc Yep, I agree with a lot of your points. I'm in the middle of updating the startunicorn command right now and should hopefully get this change released in the next few days.