Allow case sensitive search

Added checkbox to enable case sensitive search
Used Multi-field mapping to map 'content' field, once when it's analyzed
using Standard analyzer and once when it's analyzed using
analyzer similar to Standard analyzer with no lowercase and stop token filter.

Run "php scripts/ttmserver-export.php --reindex" to update index mapping.

Bug: T100013
Change-Id: I07ffa2f6eff2b905caaccca781fe438d91da65d7