[#128] Add drupal/token 8.1.x-dev as dependency to ensure code compatibility

[#113] Add tests for patterns with language conditions

Remove debug() statement

Pattern config entities

[#10] Port patterns from config objects to config entities

Plus:
* Small improvements suggested by Berdir.
* Make sure that the langcode is a valid machine-name. For example,
  Chinese traditional has a langcode zh-hant, which is not valid for a
  machine name.

Don't expect Pathauto to delete patterns on bundle deletion

The Drupal 7 version of Pathauto had logic to evaluate a bundle
being deleted and see if there were matching patterns that had
to be removed as well. This is something that we don't see a
real need for. Instead, we will let the site administrator
to clean up patterns manually after removing a bundle.

Fix form redirection after bulk delete

[#79] Update README.md

Fix PathautoUiTest test

* Remove obsolete references.
* Adjust functions that changed.

Now that patterns are config entities, the UI tests were failing.
On top of that, the Add form has an Ajax interaction to select the
pattern type, which is covered too.

Use the appropriate theme call to render link to show token tree

The dialog option for token browser is not used and is going to be
removed in https://www.drupal.org/node/2640138. This commit changes the
usages to the correct and more appropriate theme function.