fix #1677 remove datastore impl

src/main/java/org/codelibs/fess/ds/AbstractDataStore.java

src/main/java/org/codelibs/fess/ds/DataStore.java

src/main/java/org/codelibs/fess/ds/DataStoreFactory.java

...ibs/fess/ds/callback/FileListIndexUpdateCallbackImpl.java

...va/org/codelibs/fess/ds/callback/IndexUpdateCallback.java

...rg/codelibs/fess/ds/callback/IndexUpdateCallbackImpl.java

...main/java/org/codelibs/fess/ds/impl/CsvDataStoreImpl.java

.../java/org/codelibs/fess/ds/impl/CsvListDataStoreImpl.java

...java/org/codelibs/fess/ds/impl/DatabaseDataStoreImpl.java

src/main/java/org/codelibs/fess/ds/impl/EsDataStoreImpl.java

...n/java/org/codelibs/fess/ds/impl/EsListDataStoreImpl.java

...ava/org/codelibs/fess/ds/impl/GitBucketDataStoreImpl.java

...ain/java/org/codelibs/fess/ds/impl/JsonDataStoreImpl.java

src/main/java/org/codelibs/fess/helper/DataIndexHelper.java

src/main/resources/fess_ds.xml

.../org/codelibs/fess/ds/impl/DatabaseDataStoreImplTest.java

...org/codelibs/fess/ds/impl/GitBucketDataStoreImplTest.java