fix #596 convert to \0020

src/main/resources/fess_indices/fess/ja/mapping.txt

@@ -14,7 +14,7 @@
 #   See the License for the specific language governing permissions and
 #   limitations under the License.
 
-　 => \u0020
+\u0009,\u000A,\u000B,\u000C,\u000D,\u001C,\u001D,\u001E,\u001F,\u00A0,\u1680,\u180E,\u2000,\u2001,\u2002,\u2003,\u2004,\u2005,\u2006,\u2007,\u2008,\u2009,\u200A,\u200B,\u202F,\u205F,\u3000,\uFEFF => \u0020
 ~,˜,῀,⁓,∼,∿,～ => 〜
 
 Ａ => A