Fix requirejs for other locations than apps/

[juliushaertl]

Fix for https://github.com/owncloud/mail/issues/1163

This will use a dynamic baseUrl for require.js to make the mail app work within other app folders than apps/.

[mention-bot]

@juliushaertl, thanks for your PR! By analyzing the annotation information on this pull request, we identified @ChristophWurst and @Gomez to be potential reviewers

[ChristophWurst]

@juliushaertl @Gomez what are the steps to test this?

[juliushaertl]

@ChristophWurst You need to add a secound path to the apps_path config.php (https://github.com/nextcloud/server/blob/master/config/config.sample.php#L689-L703)

Install the mail app into the additional apps path, enable it and try to access it.

Without the patch, require.js tries to load all javascript files from "apps/mail/js/..:" but they are stored in e.g. "apps-extra/mail/js/..."

[ChristophWurst]

👍 works very nicely, thanks a lot 🚀