Bug 20073: Move Elasticsearch configs to yaml files and improve the default settings.

Bug 20073: Move Elasticsearch configs to yaml files and improve the default settings.

Improvements:
1) Index settings moved from code to etc/searchengine/elasticsearch/index_config.yaml. An alternative can be specified in koha-conf.xml.
2) Field settings moved from code to etc/searchengine/elasticsearch/field_config.yaml. An alternative can be specified in koha-conf.xml.
3) mappings.yaml has been moved from admin/searchengine/elasticsearch to etc/searchengine/elasticsearch. An alternative can be specified in koha-conf.xml.
4) Default settings have been improved to remove punctuation from phrases used for sorting etc.
5) State variables are used for storing configuration to avoid parsing it multiple times.
6) A possibility to reset the fields too has been added to the reset operation of mappings administration.
7) mappings.yaml has been moved from admin/searchengine/elasticsearch to etc/searchengine/elasticsearch.
8) An stdno field type has been added for standard identifiers.

To test:
1) Run tests in t/Koha/SearchEngine/Elasticsearch.t
2) Clear tables search_fields and search_marc_map
3) Go to admin/searchengine/elasticsearch/mappings.pl?op=reset&i_know_what_i_am_doing=1
4) Verify that admin/searchengine/elasticsearch/mappings.pl displays the mappings properly, including ISBN and other standard number fields.
5) Index some records using the -d parameter with misc/search_tools/rebuild_elastic_search.pl to recreate the index
6) Verify that you can find the records
7) Put <elasticsearch_index_mappings>non_existent</elasticsearch_index_mappings> to koha-conf.xml
8) Verify that admin/searchengine/elasticsearch/mappings.pl?op=reset&i_know_what_i_am_doing=1 fails because it can't find non_existent.
9) Copy etc/searchengine/elasticsearch/mappings.yaml to a new location and make elasticsearch_index_mappings setting in koha-conf.xml point to it.
10) Make a change in the new mappings.yaml.
11) Clear table search_fields (mappings reset doesn't do it yet, see bug 20248)
12) Go to admin/searchengine/elasticsearch/mappings.pl?op=reset&i_know_what_i_am_doing=1
13) Verify that the changes you made are now visible in the mappings UI

Signed-off-by: Nicolas Legrand <nicolas.legrand@bulac.fr>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>