Bug 23137: Add reset option to rebuild_elasticsearch.pl

Bug 23137: Add reset option to rebuild_elasticsearch.pl

Setup:
1 - Be using Elasticsearch
2 - Reload mappings from the db
    Admin->Search configuration
    Reset Mappings
3 - Reindex ES and confirm searching is working

To test:
1 - Apply patch
2 - Alter your mappings file for elastic (just change a description for a field)
3 - perl misc/search_tools/rebuild_elasticsearch.pl -r -v
    Verbose not necessary, but good for letting you know things are progressing
4 - Confirm the mapping change shows in the interface
5 - Confirm reindex worked and searching is working

Signed-off-by: Andrew Fuerste-Henry <andrew@bywatersolutions.com>
Signed-off-by: Jonathan Druart <jonathan.druart@bugs.koha-community.org>
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>