Better Search Replace

Medium risk: 6 changed templates, 1 removed method, 1 removed class.

• BSR_DB::mysql_escape_mimic() was removed.
• The class BSR_i18n was removed. Code that instantiates or extends it will fatal.
• The template includes/class-bsr-templates-helper.php changed. Any theme override of it is now out of date and will miss the change.
• The template templates/bsr-dashboard.php changed. Any theme override of it is now out of date and will miss the change.
• The template templates/bsr-help.php changed. Any theme override of it is now out of date and will miss the change.
• The template templates/bsr-search-replace.php changed. Any theme override of it is now out of date and will miss the change.
• The template templates/bsr-settings.php changed. Any theme override of it is now out of date and will miss the change.
• The template templates/sidebar.php changed. Any theme override of it is now out of date and will miss the change.