CRM-19303 - Drupal - Fix computation of civicrm.files on multisite

[totten]

Description

Improve computation of [civicrm.files] URL and path when using Drupal
multisite.

A good way to test this is to open multiple tabs:

• Open civicrm/admin/setting/url?reset=1 (one tab for each site)
• Open civicrm/admin/setting/path?reset=1 (one tab for each site)
• In each tab, click the "?" help icon and view the variable definitions

Before

The [civicrm.files] path/URL would always return the default
(e.g. http://example.org/sites/default/civicrm/files).

The path and URL for [civicrm.files] and [civicrm.root] are always computed.

After

If a folder named sites/{$NAME}/civicrm/files exists, it
will be used. Otherwise, the folder sites/default/files/civicrm
will be used.

The path and URL for [civicrm.files] and [civicrm.root] are computed by default. However, as a last-resort, you can explicitly set these variables in civicrm.settings.php, as in:

$GLOBALS['civicrm_paths']['civicrm.files'] = array(
  'path' => '/var/www/dmaster/civifiles/',
  'url' => 'http://dmaster.l/civifiles/',
);

---

• CRM-19303: CKEditor configuration can't be edited on a Drupal multisite installation

[seamuslee001]

@totten I tested this on AUG's system last night and appeared to work for us I couldn't see any obvious issues