Allow Solr backends to use different uniqueKey values.
Resolves VUFIND-877.
Merge pull request #24 from vufind-org/custom-solr-uniquekey

Allow Solr backends to use different uniqueKey values.
Fixed variable initialization.
Check GET parameters for ids to save into a new list and for list deletion confirmation.
Bug fix: unknown function forRoute -> fromRoute.
Refactored spellcheck to listener.
Resolves VUFIND-840.
Added note about facet caching.
Do not quote onephrase value for single words.
Progress on VUFIND-428.
Merge pull request #25 from vufind-org/spellcheck-refactor

Refactored spellcheck to listener.
Fix author information in docstring
Use search service event identifier constants

* InjectSpellingListener.php (attach): Use search service
  event identifier constants.
Merge branch 'master' of https://github.com/vufind-org/vufind
solr sharding should be used in all operations (MLT, retrieve record), not only for searches