This patch automatically configures reindexing of the search table when the
table is dropped and recreated.

* Reindexing did not properly flush the last batch of items to the search
  therefore reindexing would always miss the last few items.
* Creating a new html thread entry with inline images resulted in empty
  search content
* HTML tag stripping in HtmlThreadBody::getSearchable() would result in
  missing white space between some words, resulting in poor searchable
  content

Especially on Galera clusters, search indexing with MyISAM tables will cause
unstable clusters and loss of data. For standalone clusters using MySQL 5.6
or MariaDB 10.0, the database default table storage engine can be used,
since either support fulltext indexing.

This fixes hits when using the MySQL full text search backend

Furthermore, revamp the __cdata system to better support multiple selection
fields. Drop the `.._id` fields and use a coalesce of the ID value of the
entry value or the entry value itself. For JSON backed fields, strip some
JSON characters to result in a comma-separated list.

The search engine now uses MySQL FIND_IN_SET to analyze a search selection
in advanced searches. Also, interaction with the MySQL full text search
backend is fully supported.

Fix search backend to use the new statuses

Make table prefix consistent