Import VuFindSearch module
Import Search/BackendManager and associated classes
Initialize BackendManager in central Bootstrapper
Load VuFindSearch module
Load module `VuFindSearch' before main module
Fix incorrect method name

* VuFind/Search/Listener/NormalizeSolrSort.php (onSearchPre): Fix
incorrect method name.
Improve handling of indices in SOLR response

* VuFindSearch/Backend/Solr/Response/Json/RecordCollection.php
(getFacets): Fix wrong index in deserialized SOLR response.
(__construct): Use template to ensure existence of certain response
keys.
($template): Template of deserialized SOLR response.
Enable spellcheck if dictionary, create spelling query

* VuFindSearch/Backend/Solr/QueryBuilder.php
(createSpellcheckQuery): New function. Create spelling query.
(build): Enable spellcheck if dictionary, use new function.
New class: Iteratable NamedList `arrarr'

* VuFindSearch/Backend/Solr/Response/Json/NamedList.php: New
class. Iteratable NamedList `arrarr'.
New class: SOLR Spellcheck information

* VuFindSearch/Backend/Solr/Response/Json/Spellcheck.php: New
class. SOLR Spellcheck information.
Adjust path to ZF2 for VuFindSearch unit tests
Make SOLR parameter `fl' part of the query invariants

* VuFindSearch/Backend/Solr/Connector.php (getQueryInvariants)
(search): Make SOLR parameter `fl' part of the query invariants.
Define WidgetInterface

* VuFind/Controller/Widget/WidgetInterface.php: New interface.

A Widget is a special type of controller plugin comparable to a web
portal Portlet. It is a self-contained application component that is
interacted and interacts with the main application. The key feature of
a Widget is its capability to represent its internal state as a set of
query parameters.
Define FacetInterface

* VuFind/Controller/Widget/Solr/FacetInterface.php: New interface.
New class: Represent SOLR facet information

* VuFindSearch/Backend/Solr/Response/Json/Facets.php: New
class. Represent SOLR facet information.
Fix path to ZF2 library

* ../tests/unit-tests/phpunit.xml: Fix path to ZF2 library.
Fix docstring of fields property

* VuFindSearch/Backend/Solr/Response/Json/Facets.php: Fix docstring of
  fields property.
Import Zend\Stdlib\Parameters

* VuFind/Controller/Widget/WidgetInterface.php: Import
  Zend\Stdlib\Parameters.
New function: Render widget in specified format

* VuFind/Controller/Widget/WidgetInterface.php (render): New
function. Render widget in specified format.
Revert "New function: Render widget in specified format"

This reverts commit 87bb7a40d3b2e03d3fd536eb303656115fde2b6c.