Updates to date indexing and search processing

Updates to date indexing and search processing

Summary of Koha 3.0 date indexing for MARC21:

Index                   Expected format         Notes
-----------------------------------------------------
date-entered-on-file    [yymmdd]                (008/0-5, indexed in word and sort indexes)
copydate                [yyyy]                  (260$c, indexed in word and sort indexes)
acqdate                 [yyyy-mm-dd]            (952$d, indexed in date,word,sort indexes)
pubdate                 [yyyy]                  (008/7-10, indexed in year,word,sort indexes)

Template Search Parameters Tested:
        limit-yr (either yyyy or yyyy-yyyy) (added processing for ge le, structure attribute st-numeric, etc.)
        yr pubdate (yyyy)
        acqdate,st-date-normalized (yyyy-mm-dd)

Template Sort Parameters Tested:
        pubdate_dsc
        pubdate_asc
        acqdate_dsc
        acqdate_asc

Signed-off-by: Joshua Ferraro <jmf@liblime.com>